IEC 61643
SPD Calculator
Choose a starting surge protective device type for AC, DC, or PV systems based on exposure, installation point, and system earthing.
Lightning exposure · Installation point · System earthing→SPD type
Open calculatorVIOX engineering tools
Electrical calculators for practical design, selection, and verification.
Fast reference checks for electrical engineers, panel builders, distributors, and OEMs.
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Popular tools
Most-used calculators from the existing library.
Voltage Drop Calculator
Estimate voltage drop by current, conductor length, material, cross-section, and phase system.
Current · Length · Conductor size→Drop in V and %
Open calculatorCable Size Calculator
Find a reference conductor size from load current, sizing factor, conductor material, and installation severity.
Load current · Installation · Material→Reference conductor size
Open calculatorNEC Chapter 9
Conduit Fill Calculator
Calculate conduit fill percentage from pathway type, trade size, cable outside diameter, and cable quantity.
Conduit · Cables · Run type→Fill % and passing size
Open calculatorDC Voltage Drop Calculator
Check DC voltage drop for 12 V, 24 V, 48 V, control, LED, battery, and PV accessory circuits using AWG conductor resistance.
Current · One-way length · AWG→DC drop in V and %
Open calculatorAWG Wire Size Calculator
Find the smallest AWG conductor that passes both reference ampacity and voltage-drop checks.
AWG or area · Conductor material · Application→Wire dimensions and current
Open calculatormm² to AWG & AWG to mm² Converter
Convert conductor cross-sectional area between metric mm² and American Wire Gauge, with nearest and not-smaller standard-size references.
Area or AWG · Conversion direction→Equivalent conductor size
Open calculatorCircuit Breaker Size Calculator
Estimate a standard MCB or MCCB current rating from load power, voltage, phase, power factor, and sizing factor.
Power · Voltage · Load type→Standard breaker rating
Open calculatorHow it works
Four steps from load to verification.
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Browse by category
Jump directly to the engineering task.
Electrical Fundamentals & Circuit Analysis
Core formulas, phase power, resistance, circuits, and units
→Cable, Wire & Voltage Drop Tools
Conductor size, ampacity, voltage drop, and fault withstand
→Cable Management & Installation
Conduit, tray, glands, lugs, routing, and cable entry
→Circuit Protection & Grounding
Breakers, fuses, fault current, grounding, and arc flash
→Power Systems & Distribution
Transformers, demand, ATS, busbars, power quality, and generators
→Panels, Enclosures & Thermal
Panel heat, terminals, clearances, creepage, and enclosure ratings
→Motors, Contactors & Drives
Motor current, starting, contactors, voltage quality, and VFDs
→Solar, Battery & Backup Power
PV strings, batteries, inverters, UPS, charging, and backup energy
→Surge & Lightning Protection Tools
Lightning exposure, SPD selection, coordination, and backup protection
→EV Charging Tools
Charging time, cost, current, demand, and feeder planning
→Lighting Design
Lux, lumens, fixtures, circuits, efficiency, and emergency lighting
→Library
All calculators
Every calculator, grouped by category.
Electrical Fundamentals & Circuit Analysis
Core formulas, phase power, resistance, circuits, and units
kW, kVA and Amp Calculator
Convert kW to amps, kVA to amps, amps to kW, kW to kVA, or kVA to kW. Choose a task and enter only the values it needs.
Power · Voltage · Phase→kW, kVA or current
Open calculatorThree Phase Current Calculator
Calculate three-phase current from kW or kVA, line voltage, power factor, and efficiency.
kW or kVA · Line voltage · Power factor→Three-phase current
Open calculatorPower Factor Calculator and Correction
Analyze active, reactive, and apparent power or calculate the capacitor-bank kvar needed to improve power factor.
kW · Existing PF · Target PF→kVAR and correction bank
Open calculatorRMS, Peak & Peak-to-Peak Voltage Calculator
Convert any one RMS, peak, peak-to-peak, or rectified-average voltage into the other three values for a sine, square, or triangle wave.
Waveform · Known voltage type · Voltage value→RMS, peak, peak-to-peak and average
Open calculatorResistor Wattage Calculator
Calculate resistor dissipation from V and R, I and R, or V and I, apply a two-times engineering margin, and select the next common power rating.
V and R, I and R, or V and I→Dissipation and suggested rating
Open calculatorDelta-Wye Conversion Calculator
Convert balanced or unbalanced Delta and Wye resistor networks with explicit RAB, RBC, RCA, RA, RB, and RC terminal mapping.
Conversion direction · Balance · Branch resistances→Equivalent network resistances
Open calculatorRC Circuit and Time Constant Calculator
Calculate RC time constant, cutoff frequency, charging and discharging voltage, capacitive reactance, impedance, gain, and phase at one frequency.
Resistance · Capacitance · Step voltage→RC Circuit
Open calculatorRLC Impedance and Resonance Calculator
Calculate series or parallel RLC reactance, impedance, admittance, current, phase angle, power factor, resonance frequency, and Q factor.
RMS source voltage · Frequency · Resistance→RLC Impedance
Open calculatorCurrent Divider Calculator
Split a known total current across two to six parallel resistive branches and calculate equivalent resistance, common voltage, branch current, and branch power.
Total current · Branch resistance R1 · Branch resistance R2→Current Divider
Open calculatorCapacitor Reactance and Energy Calculator
Calculate capacitive reactance, RMS current, stored energy, charge, peak current screen, and series or parallel equivalent capacitance.
Capacitance · Frequency · Applied voltage→Capacitor
Open calculatorInductor Reactance and Energy Calculator
Calculate inductive reactance, RMS current, stored magnetic energy, time constant, and series or parallel equivalent inductance.
Inductance · Frequency · Applied RMS voltage→Inductor
Open calculatorCurrent Shunt Calculator
Size or verify a DC current shunt from rated current and millivolt drop, including resistance, power loss, burden voltage, and meter scaling.
Rated shunt current · Rated shunt drop · Current to verify→Current Shunt
Open calculatorThree-Phase Power Calculator
Calculate balanced three-phase active power, apparent power, reactive power, current, phase angle, and power-factor improvement effects.
Line-to-line voltage · Line current · Active power→Three-Phase Power
Open calculatorPower, Energy & Time Calculator
Enter any two of power, energy, and operating time to calculate the third with automatic electrical-unit conversion.
Any two: power, energy, time→Remaining quantity
Open calculatorVoltage Divider Calculator with Load
Calculate a two-resistor voltage divider, solve for either resistor, or include load resistance to quantify output error and resistor power.
Input voltage · Upper resistor R1 · Lower resistor R2→Voltage Divider
Open calculatorIEC 60664-1
PCB Conductor Spacing Calculator
Estimate a PCB conductor-spacing reference from voltage and conductor environment, or calculate the maximum reference voltage for an available spacing.
Voltage between conductors · Voltage basis · Available edge-to-edge spacing→PCB Conductor Spacing
Open calculatorOhm's Law Calculator
Enter any two of voltage, current, resistance, and power to calculate the other two electrical quantities.
Any two: V, I, R, P→Remaining electrical values
Open calculatorWatts to Amps and Volts Calculator
Convert watts, amps, and volts for DC, single-phase, or three-phase systems with common voltage presets.
Any two: W, A, V · Phase and PF→Remaining values
Open calculatorSeries and Parallel Resistor Calculator
Calculate equivalent resistance, current, and voltage or current division for up to four resistors.
Connection · R1 · R2→Resistor Network
Open calculatorElectrical Unit Converter
Convert power and energy units in either direction, or calculate DC, single-phase, and three-phase current from power.
Value · From unit · To unit→Converted electrical value
Open calculatorkW to HP Calculator and HP to kW Converter
Convert kilowatts to horsepower or horsepower to kilowatts using mechanical, metric, or electrical horsepower definitions.
Power · Horsepower standard→kW to HP
Open calculatorAmps to kW Calculator
Convert amps to kW with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Current · Voltage · System→amps to kW
Open calculatorkW to Amps Calculator
Convert kW to amps with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Real power · Voltage · System→kW to amps
Open calculatorAmps to kVA Calculator
Convert amps to kVA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Current · Voltage · System→amps to kVA
Open calculatorkVA to Amps Calculator
Convert kVA to amps with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power · Voltage · System→kVA to amps
Open calculatorAmps to VA Calculator
Convert amps to VA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Current · Voltage · System→amps to VA
Open calculatorVA to Amps Calculator
Convert VA to amps with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power · Voltage · System→VA to amps
Open calculatorAmps to Volts Calculator
Convert amps to volts with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Current · Apparent power→amps to volts
Open calculatorVolts to Amps Calculator
Convert volts to amps with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Voltage · Apparent power→volts to amps
Open calculatorAmps to Watts Calculator
Convert amps to watts with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Current · Voltage · System→amps to watts
Open calculatorWatts to Amps Calculator
Convert watts to amps with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Real power · Voltage · System→watts to amps
Open calculatorAmps to HP Calculator
Convert amps to HP with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Current · Voltage · System→amps to HP
Open calculatorHP to Amps Calculator
Convert HP to amps with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Motor output · Voltage · System→HP to amps
Open calculatorHP to kVA Calculator
Convert HP to kVA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Motor output · System · Power factor→HP to kVA
Open calculatorkVA to HP Calculator
Convert kVA to HP with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power · System · Power factor→kVA to HP
Open calculatorkVA to kW Calculator
Convert kVA to kW with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power · Power factor→kVA to kW
Open calculatorkW to kVA Calculator
Convert kW to kVA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Real power · Power factor→kW to kVA
Open calculatorkVA to VA Calculator
Convert kVA to VA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power→kVA to VA
Open calculatorVA to kVA Calculator
Convert VA to kVA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power→VA to kVA
Open calculatorkVA to Watts Calculator
Convert kVA to watts with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power · Power factor→kVA to watts
Open calculatorWatts to kVA Calculator
Convert watts to kVA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Real power · Power factor→watts to kVA
Open calculatorkW to VA Calculator
Convert kW to VA with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Real power · Power factor→kW to VA
Open calculatorVA to kW Calculator
Convert VA to kW with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Apparent power · Power factor→VA to kW
Open calculatorVolts to Watts Calculator
Convert volts to watts with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Voltage · Current · System→volts to watts
Open calculatorWatts to Volts Calculator
Convert watts to volts with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Real power · Current · System→watts to volts
Open calculatorkW to kWh Calculator
Convert kW to kWh with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Power · Time→kW to kWh
Open calculatorkWh to kW Calculator
Convert kWh to kW with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Energy · Time→kWh to kW
Open calculatorkWh to Watts Calculator
Convert kWh to watts with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Energy · Time→kWh to watts
Open calculatorWatts to kWh Calculator
Convert watts to kWh with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Power · Time→watts to kWh
Open calculatorIEC 60063
LED Resistor Calculator
Calculate the exact LED series resistor, nearest E12 and E24 values, actual current, dissipation, and a practical resistor power rating.
Supply · LED Vf · Current→Resistor and power rating
Open calculatorIEC 60062
Resistor Color Code Calculator
Decode 4, 5, or 6-band resistor colors or convert a resistance value into a color-band sequence, including tolerance and temperature coefficient.
Band colors or resistance→Resistance, tolerance and bands
Open calculatorEIA-96
SMD Resistor Code Calculator
Decode three-digit and four-digit SMD resistor codes, R decimal markings, and EIA-96 codes into a nominal resistance value.
SMD code→Resistance value
Open calculatorSimple Power Factor Calculator
Calculate power factor, phase angle, and reactive power from any solvable pair of kW, kVA, kVAR, voltage, and current values.
kW · kVA · kVAR or V and A→PF, phase angle and kVAR
Open calculatorCable, Wire & Voltage Drop Tools
Conductor size, ampacity, voltage drop, and fault withstand
Voltage Drop Calculator
Estimate voltage drop by current, conductor length, material, cross-section, and phase system.
Current · Length · Conductor size→Drop in V and %
Open calculatorCable Size Calculator
Find a reference conductor size from load current, sizing factor, conductor material, and installation severity.
Load current · Installation · Material→Reference conductor size
Open calculatorDC Voltage Drop Calculator
Check DC voltage drop for 12 V, 24 V, 48 V, control, LED, battery, and PV accessory circuits using AWG conductor resistance.
Current · One-way length · AWG→DC drop in V and %
Open calculatorAWG Wire Size Calculator
Find the smallest AWG conductor that passes both reference ampacity and voltage-drop checks.
AWG or area · Conductor material · Application→Wire dimensions and current
Open calculatormm² to AWG & AWG to mm² Converter
Convert conductor cross-sectional area between metric mm² and American Wire Gauge, with nearest and not-smaller standard-size references.
Area or AWG · Conversion direction→Equivalent conductor size
Open calculatorNEC 310.16NEC 110.14
Copper to Aluminum Conductor Conversion Calculator
Find the smallest listed aluminum conductor with at least the copper ampacity in NEC Table 310.16 at 75 or 90 degrees Celsius.
Copper size · Temperature column→Equivalent aluminum size
Open calculatorWire Resistance Calculator
Calculate one-conductor resistance from copper or aluminum size, conductor length, and temperature, with results in ohms, Ω/1000 ft, and Ω/km.
Material · Conductor size · Length and temperature→Resistance and normalized values
Open calculatorIEC 60364-5-52
Cable Derating Factor Calculator
Combine ambient-temperature, grouping, installation, and soil factors to estimate corrected cable ampacity.
Reference cable ampacity · Ambient temperature · Conductor insulation→Cable Derating
Open calculatorIEC 60364-5-54
Protective Conductor Size Calculator
Calculate minimum protective-conductor cross-section using the IEC adiabatic equation and a user-selected material k value.
Earth fault current · Protective-device clearing time · Conductor k value→PE Conductor
Open calculatorCable Short-Circuit Thermal Withstand Calculator
Check cable short-circuit thermal withstand using conductor area, fault current, duration, and material k value.
Fault current · Clearing time · Conductor→Thermal withstand check
Open calculatorCable Management & Installation
Conduit, tray, glands, lugs, routing, and cable entry
NEC Chapter 9
Conduit Fill Calculator
Calculate conduit fill percentage from pathway type, trade size, cable outside diameter, and cable quantity.
Conduit · Cables · Run type→Fill % and passing size
Open calculatorCable Gland Size Calculator
Select a cable gland by cable outside diameter or check Metric, PG, NPT, and G/BSPP entry threads.
Cable OD · Thread family · Environment→Gland size and thread
Open calculatorCable Lug Selection Calculator
Select a preliminary cable-lug material, conductor marking, stud hole, palm style, finish, and connection method.
Conductor size system · Metric conductor size · AWG conductor size→Cable Lug
Open calculatorConduit Bending Calculator
Calculate field marks for offsets, three-point saddles, four-point saddles and 90-degree stubs using documented bender charts.
Bend type · Offset depth · Angle→Mark spacing and shrink
Open calculatorCable Pulling Tension Calculator
Estimate straight-section pulling tension, capstan tension after a bend, sidewall pressure, and allowable-tension utilization for a simplified cable pull.
Total cable weight · Straight pulling length · Coefficient of friction→Cable Pulling Tension
Open calculatorNEC 392
Cable Tray Fill and Sizing Calculator
Calculate cable tray area fill, single-layer width, reserve capacity, remaining space, cable weight, and a preliminary tray-width requirement.
Check method · Cable tray type · Usable tray width→Cable Tray Fill
Open calculatorCircuit Protection & Grounding
Breakers, fuses, fault current, grounding, and arc flash
Circuit Breaker Size Calculator
Estimate a standard MCB or MCCB current rating from load power, voltage, phase, power factor, and sizing factor.
Power · Voltage · Load type→Standard breaker rating
Open calculatorShort Circuit Current Calculator
Estimate available transformer secondary fault current from transformer kVA, impedance, voltage, phase, and optional utility fault contribution.
Transformer kVA · Impedance · Voltage→Fault current in kA
Open calculatorFuse Sizing & Selection Calculator
Size a preliminary gG, aM, or gPV fuse and check load current, cable ampacity, breaking capacity, motor starting duty, or PV module limits.
Load current · Fuse class · Application→Fuse rating and checks
Open calculatorMCB Inrush Compatibility Checker
Compare equipment inrush current with IEC-style B, C, or D magnetic-trip bands and check whether available fault current supports instantaneous operation.
MCB rated current · Selected curve · Peak inrush current→MCB Inrush
Open calculatorRCD & RCBO Selection Calculator
Select a starting residual-current type, sensitivity, poles, rated current, overcurrent curve, and breaking capacity for common loads.
Application · Device function · Supply conductors→RCD / RCBO
Open calculatorUL 508A Supplement SB
Assembly SCCR Calculator
Find the weakest entered power-circuit component and the unenhanced assembly SCCR. Use verified ratings or the documented terminal-block default.
Components · Component SCCR · Rating basis→Assembly SCCR and weakest link
Open calculatorIEC 60255
IDMT Relay Trip-Time Calculator
Calculate IEC 60255 standard, very, and extremely inverse relay trip times, then compare upstream and downstream grading margin against 0.30 seconds.
Curve and pickup · Fault current · Upstream and downstream TMS→Trip times and grading margin
Open calculatorGrounding Resistance Calculator
Estimate single vertical ground-rod resistance and a preliminary multiple-rod result from soil resistivity, rod length, diameter, count, and spacing.
Soil resistivity · Rod length · Rod diameter→Ground Rod Resistance
Open calculatorCircuit Breaker Selectivity and Cascading Checker
Screen upstream and downstream breaker rating, curve, breaking capacity, and fault-current coordination.
Upstream breaker rating · Upstream trip curve · Upstream breaking capacity→Breaker Selectivity
Open calculatorEarth Fault Loop Impedance Calculator (Zs)
Calculate actual earth fault loop impedance and compare it with a device-based maximum Zs input.
Supply voltage · Loop path · Conductor data→Zs and disconnection check
Open calculatorIEEE 1584-2018
Arc Flash Incident Energy Calculator – IEEE 1584-2018
Calculate IEEE 1584-2018 arcing current, incident energy, and arc-flash boundary for normal and reduced-current clearing-time scenarios.
Three-phase open-circuit voltage · Bolted three-phase fault current · Electrode configuration→Arc Flash
Open calculatorIEC 62606
AFDD Requirement & Selection Calculator
Screen an AFDD or AFDD-RCBO requirement and check a preliminary VIOX configuration by circuit, current, curve, residual sensitivity, and fault level.
Region / rules basis · Premises / risk context · Final-circuit use→AFDD Selection
Open calculatorDC Circuit Breaker Sizing Calculator
Calculate DC design current and screen a DC MCB or MCCB for current, voltage, cable ampacity, poles, and breaking capacity.
DC application · Known load value · Maximum operating current→DC Breaker Size
Open calculatorACB Frame & LSIG Setting Calculator
Build a preliminary ACB frame and LSIG worksheet from design current, cable capacity, fault level, downstream rating, and entered pickup multiples.
Feeder design current Ib · Protected conductor ampacity Iz · Long-time pickup margin→ACB LSIG
Open calculatorCircuit Breaker Accessory Power Calculator
Calculate peak and continuous control-supply demand for shunt trips, undervoltage releases, motor operators, and other breaker accessories.
Control supply voltage · Operating coincidence · Shunt-trip quantity→Breaker Accessory VA
Open calculatorPower Systems & Distribution
Transformers, demand, ATS, busbars, power quality, and generators
Transformer Sizing Calculator
Estimate transformer kVA from connected load, demand factor, future growth, loading margin, ambient derating, and standard rating series.
Load · Power factor · Margin→Transformer kVA
Open calculatorBusbar Current Rating Calculator
Estimate busbar current from width, thickness, material, current-density reference, and derating factor.
Width · Thickness · Material→Busbar current rating
Open calculatorATS Selection Calculator
Select a preliminary ATS current rating, PC or CB class, pole arrangement, transfer-speed category, and UPS or STS requirement.
Maximum load current · ATS design factor · Supply system→ATS Selection
Open calculatorIEC 61439
Busbar Short-Circuit Force Calculator
Estimate electrodynamic force between parallel busbars from peak short-circuit current, conductor spacing, and unsupported support span.
Fault-current input · Short-circuit current · RMS-to-peak factor→Busbar Force
Open calculatorBuck-Boost Transformer Calculator
Calculate single-phase voltage correction, load current and theoretical transformed kVA. Check documented 208/230 V winding-based capacity separately.
Supply voltage · Target voltage · Load kVA→Voltage change and transformer kVA
Open calculatorNeutral Current Calculator
Estimate fundamental and third-harmonic neutral current from three phase currents, then check total neutral utilization against an optional ampacity.
Three phase currents · Third-harmonic percentages · Neutral ampacity→Fundamental, harmonic and total neutral current
Open calculatorGenerator Fuel Consumption Calculator
Estimate generator fuel use in L/hr and gal/hr, tank runtime, and hourly or daily operating cost from rated power, load factor, fuel, tank size, price, and daily hours.
Rated kW · Load and fuel · Tank and price→L/hr, gal/hr, runtime and cost
Open calculatorBranch Circuit Count Calculator
Estimate branch-circuit quantity from floor area, general load density, circuit voltage and rating, planned loading, dedicated circuits, and optional NEC dwelling circuits.
Floor area · General load density · Circuit voltage→Branch Circuit Count
Open calculatorElectrical Panel Load and Spare Capacity Calculator
Calculate panel kVA, current, utilization, spare amperes, spare kVA, phase-load unbalance, and expansion impact from entered demand loads.
Panel system · Panel voltage · Panel main rating→Panel Load
Open calculatorTransformer Impedance Calculator
Calculate transformer full-load current, ohmic impedance, R and X components, X/R ratio, and infinite-bus secondary fault current.
System · Transformer rating · Secondary voltage→Transformer Impedance
Open calculatorGenerator Sizing Calculator
Estimate generator kW and kVA from running load, largest starting step, power factor, reserve, growth, altitude, and ambient derating.
Maximum coincident running load · Load power factor · Largest additional starting step→Generator Sizing
Open calculatorIEEE 519
Harmonic and THD Calculator
Calculate THD, total RMS, individual harmonic distortion, triplen content, crest-factor screen, and neutral-current warning from harmonic magnitudes.
Fundamental H1 · 3rd harmonic · 5th harmonic→Harmonic THD
Open calculatorMaximum Demand and Diversity Calculator
Combine lighting, socket, HVAC, motor, EV, and other loads with demand and simultaneity factors.
Lighting connected load · Lighting demand factor · Socket connected load→Maximum Demand
Open calculatorNEC 220.82NEC 220.83
Residential Service Load Calculator — NEC 220.82 / 220.83
Calculate dwelling service demand using NEC 220.82 or existing-dwelling NEC 220.83(A)/(B), with nameplate loads, heating rules and service comparison.
Calculation method · Dwelling floor area · Small-appliance circuits→Residential Load
Open calculatorCT Ratio & Burden Calculator
Select a reference current-transformer ratio and calculate secondary lead, meter, relay, and total connected burden for 1 A or 5 A CT circuits.
Maximum primary current · Primary ratio margin · CT secondary rating→CT Ratio & Burden
Open calculatorPanels, Enclosures & Thermal
Panel heat, terminals, clearances, creepage, and enclosure ratings
Electrical Terminal Heating Calculator
Calculate contact power loss, voltage drop, daily heat energy, and optional temperature-rise estimate from current and contact resistance.
Load current · Contact resistance · Healthy reference resistance→Terminal Heating
Open calculatorNEC 314.16
Box Fill Calculator
Calculate required electrical box volume from conductor sizes, device yokes, internal clamps and grounding conductors using NEC 314.16.
Conductors · Yokes · Clamps→Volume, PASS or FAIL
Open calculatorNEC 314.28
Pull Box / Junction Box Sizing Calculator
Check pull box distances for straight, angle and U pulls or splices using NEC 314.28. Compare a wall or row and the spacing between connected entries.
Pull type · Raceways · Wall distance→Minimum box distance
Open calculatorIEC 60664-1
Clearance & Creepage Calculator
Estimate IEC 60664-1 minimum clearance through air and creepage along an insulating surface from voltage, overvoltage category, pollution degree, CTI group, insulation level, and altitude.
Voltage · Pollution degree · Material group→Clearance and creepage
Open calculatorIEC 60890
Enclosure Cooling & Temperature Rise Calculator
Calculate enclosure internal temperature, required fan airflow, or active cooling capacity from cabinet size, heat load, ambient conditions, insulation, solar load, and protection requirements.
Heat load · Enclosure size · Ambient→Temperature rise and airflow
Open calculatorPanel Component Heat Loss Calculator
Add breaker, contactor, drive, power-supply, transformer, and miscellaneous losses to estimate total cabinet heat load.
Breaker losses · Contactor and relay losses · VFD / drive losses→Panel Heat Loss
Open calculatorNEMA 250IEC 60529
NEMA and IP Enclosure Rating Converter
Decode IEC IP ratings, cross-reference NEMA enclosure Types to IP protection, and screen enclosure Types from location, water, dust, corrosion, oil, ice, and immersion exposure.
NEMA or IP rating · Environment→Ingress-rating cross reference
Open calculatorMotors, Contactors & Drives
Motor current, starting, contactors, voltage quality, and VFDs
NEC 430.248NEC 430.250
Motor FLA Calculator: Full Load Amps by HP & Voltage
Calculate motor full-load amps from power or look up NEC Table 430.250 three-phase and Table 430.248 single-phase values by HP and voltage.
HP or power · Voltage · Efficiency→Motor FLA
Open calculatorMotor Starter Selection Calculator
Estimate motor current, starting current, contactor duty, overload-relay range, and preliminary short-circuit protection for a motor starter.
Motor data · Motor output power · Nameplate full-load current→Motor Starter
Open calculatorNEMA MG 1
Three-Phase Voltage Unbalance Calculator
Calculate three-phase voltage unbalance, voltage-window thresholds, and select a starting VIOX FCP18 monitoring-relay function.
Measurement system · Voltage 1 · Voltage 2→Voltage Unbalance
Open calculatorNEC 430.7(B)
Motor Starting Current Calculator (Locked Rotor Amps)
Estimate motor locked-rotor amps from a nameplate NEC Code letter, or apply an editable starting-current multiplier to motor full-load amps.
HP and voltage · Code letter or FLA · Starting method→Starting kVA, LRA and range
Open calculatorIEC 60034-1NEMA MG 1
Motor Speed & Slip Calculator
Calculate induction-motor synchronous speed, slip, rotor speed and rotor frequency from poles, supply frequency and measured speed or known slip.
Poles · Frequency · Speed or slip→ns, slip, nr and fr
Open calculatorInsulation Resistance Temperature Correction Calculator
Correct a measured insulation-resistance value to a reference temperature using a selectable doubling-temperature or entered correction coefficient.
Measured insulation resistance · Measured winding or insulation temperature · Reference temperature→Insulation Resistance
Open calculatorMotor Torque Calculator
Calculate motor shaft torque, output power, input power, angular speed, and lb-ft from kW or hp, rotational speed, and efficiency.
Motor rated power · Power basis · Motor speed→Motor Torque
Open calculatorMotor Control Panel Load Calculator
Estimate an MCC or motor-control-panel feeder ampacity from the largest motor, remaining motors, non-motor load, demand, and spare capacity.
Largest motor full-load current · Sum of other motor full-load currents · Other-motor demand factor→MCC Panel Load
Open calculatorContactor Selection Calculator (AC-1 / AC-3)
Estimate a contactor current class from load type, power, voltage, utilization category, and operating frequency.
Load type · Load power · Line voltage→Contactor Selector
Open calculatorMotor Starting Voltage Drop Calculator
Estimate bus voltage dip during motor starting from motor current, starting method, transformer impedance, and feeder impedance.
Motor output power · Line voltage · Motor efficiency→Motor Start Drop
Open calculatorVFD Sizing, Protection and Panel Calculator
Estimate the minimum VFD output-current class and screen input protection, bypass contactor, filtering, braking, and panel heat requirements.
Motor rated output power · Motor rated voltage · Motor nameplate current→VFD Sizing
Open calculatorSolid State Relay Selection & Heatsink Calculator
Calculate SSR load current, minimum nameplate-current screen, conduction loss, heatsink thermal resistance, junction temperature, surge margin, and semiconductor-fuse I²t checks.
Load circuit · Known load value · Load power→SSR Selection
Open calculatorSolar, Battery & Backup Power
PV strings, batteries, inverters, UPS, charging, and backup energy
IEC 62548IEC 60364-7-712
PV Combiner Box Sizing Calculator
Size key PV combiner-box ratings from module Voc, Isc, temperature coefficient, series modules, parallel strings, cable ampacity, and lightning exposure.
Module open-circuit voltage · Voc temperature coefficient · Minimum design temperature→PV Combiner Box
Open calculatorBattery C-Rate & Runtime Calculator
Calculate battery C-rate, P-rate, nominal and usable energy, discharge current, and estimated runtime for packs or BESS projects.
Battery capacity · Voltage · Load→C-rate and runtime
Open calculatorElectrical Energy Cost Calculator
Calculate daily, monthly, and annual electricity consumption and operating cost from power, runtime, quantity, load factor, and tariff.
Rated input power · Average load factor · Operating time→Energy Cost
Open calculatorGrid-Tied Solar Panel Calculator
Estimate average daily solar production, required DC array kW, module quantity, and roof area from annual electricity use and peak sun hours.
Annual energy · Sun hours · Module rating→Array kW, modules and roof area
Open calculatorSolar Battery Bank Size Calculator
Calculate solar battery bank kWh, Ah, and battery quantity from daily energy, autonomy days, depth of discharge, system voltage, and battery capacity.
Daily load · Autonomy and DoD · System voltage→Bank kWh, Ah and battery count
Open calculatorNEC 690.8
MPPT Solar Charge Controller Sizing Calculator
Size an MPPT solar controller using 125% of string Isc, 125% of string Voc for low temperature, and the full PV array power requirement.
Modules and power · String Voc · String Isc→Controller current, voltage and PV power
Open calculatorNEC 690.8
Solar Voltage Drop Calculator
Calculate DC solar voltage drop from string Isc, one-way cable length, Vmp, and copper conductor size using a 125% design current and 2% target.
String Isc · Length and Vmp · Copper size→Voltage drop and PASS/FAIL
Open calculatorAS/NZS 4777
Voltage Rise Calculator
Calculate grid-tied inverter voltage rise from export current, complete loop resistance, and nominal voltage, with a 2% AS/NZS 4777 screening check.
Grid current · Loop resistance · Nominal voltage→Voltage rise and percentage
Open calculatorUPS Sizing Calculator
Calculate UPS VA and watt ratings with a reserve margin, then estimate backup time from battery energy, actual load, and inverter efficiency.
Load W · Power factor · Reserve and Wh→VA, W and backup minutes
Open calculatorIEEE 946
Battery Charger Sizing Calculator (IEEE 946)
Size a stationary battery charger from continuous DC load, discharged Ah, recharge time, and the largest noncontinuous load using the IEEE 946 method.
Continuous load · Discharged Ah · Recharge time→I1, I2 and charger rating
Open calculatorUPS Backup Time Calculator
Estimate UPS battery runtime from load, battery voltage and Ah, series and parallel configuration, inverter efficiency, aging, and depth of discharge.
Protected load · Battery or block voltage · Battery capacity→UPS Runtime
Open calculatorInverter Sizing Calculator
Estimate inverter continuous kW, kVA, surge rating, DC input current, AC output current, and PV DC array reference from load and design margins.
Maximum continuous AC load · Load power factor · Maximum simultaneous surge→Inverter Sizing
Open calculatorBattery Capacity Converter
Convert battery Ah, mAh, Wh, and kWh while accounting for voltage, series and parallel configuration, depth of discharge, and efficiency.
Capacity per cell or parallel unit · Capacity unit · Battery energy→Battery Capacity
Open calculatorBattery Charging Time Calculator
Calculate battery charging time from Ah and current or kWh and charger power, including charging efficiency.
Input method · Battery capacity · Charging current→Battery Charge Time
Open calculatorIEC 62548
PV String Sizing Calculator
Calculate temperature-corrected PV string voltage and the allowable module count for an inverter MPPT window.
Module Voc at STC · Module Vmpp at STC · Voc temperature coefficient→PV String Size
Open calculatorOff-Grid Solar System Sizing Calculator
Estimate PV array, battery-bank capacity, and inverter power from daily energy, sun hours, autonomy, and system voltage.
Daily energy use · Peak sun hours · Overall system efficiency→Off-Grid Solar
Open calculatorIEEE 485
Stationary Battery and DC System Sizing Calculator
Estimate stationary battery Ah, cell count, bank energy, parallel strings, peak discharge rate, charger current, and DC protection current.
Daily energy · Autonomy · Depth of discharge→Required battery capacity
Open calculatorIEC 60947-3
PV DC Isolator Sizing Calculator
Calculate cold-condition PV array voltage and design current, then screen a DC isolator voltage, current, utilization category, and pole arrangement.
Module Voc at STC · Voc temperature coefficient · Minimum cell temperature→PV DC Isolator
Open calculatorPV DC ATS Sizing Calculator
Calculate DC design current and organize voltage, source, transition, pole, and candidate-rating checks for a PV or battery DC transfer switch.
DC source application · Known load value · Maximum transferred power→PV DC ATS
Open calculatorAh to kWh Calculator
Convert Ah to kWh with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Battery capacity · Voltage→Ah to kWh
Open calculatorkWh to Ah Calculator
Convert kWh to Ah with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Battery energy · Voltage→kWh to Ah
Open calculatorAh to Wh Calculator
Convert Ah to Wh with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Battery capacity · Voltage→Ah to Wh
Open calculatorWh to Ah Calculator
Convert Wh to Ah with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Battery energy · Voltage→Wh to Ah
Open calculatormAh to Wh Calculator
Convert mAh to Wh with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Battery capacity · Voltage→mAh to Wh
Open calculatorWh to mAh Calculator
Convert Wh to mAh with the correct phase, power-factor, efficiency, time, or voltage basis where the selected conversion requires it.
Battery energy · Voltage→Wh to mAh
Open calculatorSurge & Lightning Protection Tools
Lightning exposure, SPD selection, coordination, and backup protection
IEC 61643
SPD Calculator
Choose a starting surge protective device type for AC, DC, or PV systems based on exposure, installation point, and system earthing.
Lightning exposure · Installation point · System earthing→SPD type
Open calculatorIEC 61643
Advanced SPD Selection Calculator
Select a preliminary SPD type, connection arrangement, Uc or Ucpv range, discharge-duty level, and backup-protection checks.
System · Nominal working voltage · Earthing arrangement→Advanced SPD
Open calculatorIEC 62305
Lightning Risk Assessment Calculator
Estimate a simplified lightning exposure score from building collection area, location, thunderstorm activity, and incoming lines.
Building length · Building width · Building height→Lightning Risk
Open calculatorSPD Backup Fuse Selection Calculator
Screen an SPD backup fuse or MCB rating from the SPD datasheet maximum backup protection and prospective fault current.
SPD duty · SPD datasheet maximum backup fuse · Existing upstream protective device→SPD Backup Fuse
Open calculatorEV Charging Tools
Charging time, cost, current, demand, and feeder planning
IEC 61851
EV Charger Load Calculator
Estimate EV charger current and total distribution load from charger power, phase, quantity, and simultaneity.
Charger power · Phase · Quantity→Charger current and demand
Open calculatorEV Charging Time and Cost Calculator
Estimate EV charging time, delivered energy, wall energy, and cost from battery state of charge and charger power.
Usable battery capacity · Starting state of charge · Target state of charge→EV Charge Time
Open calculatorLighting Design
Lux, lumens, fixtures, circuits, efficiency, and emergency lighting
Emergency Lighting Battery Calculator
Estimate emergency-lighting battery Wh and Ah from fixture load, duration, efficiency, depth of discharge, aging, temperature, and design margin.
Emergency input power per fixture · Required emergency duration · Nominal battery voltage→Emergency Lighting
Open calculatorLighting Circuit Load Calculator
Calculate connected lighting watts, input VA, current, energy, circuit quantity, loading per circuit, and LED driver inrush screening.
Input power per fixture · Circuit voltage · Driver power factor→Lighting Circuit
Open calculatorLighting Calculator: Lux, Lumens and Fixtures
Calculate required lumens, LED fixture quantity, achieved illuminance, connected watts, current, and preliminary lighting-circuit count.
Space or task · Required illuminance · Area input→Lighting
Open calculator