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Electrical Load Calculator

By · Updated Aug 2026

Combine up to six equipment loads on one power basis, then convert the total to current, kW, and kVA for single-phase or balanced three-phase power.

W/VA
W/VA
V
Single-phase uses system voltage. Balanced three-phase uses line-to-line RMS voltage.
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How to Use

  1. Choose watts or VA - Use watts when you know real power. Use VA when the source/nameplate gives apparent power.
  2. Enter up to six loads - Add the equipment values you want to combine. All entries use the selected watts or VA basis, and only positive entries are included.
  3. Set voltage and phase - For three-phase, the calculator uses the balanced line-to-line √3 relationship.
  4. Enter power factor when known - Leave power factor blank to use 1.00. For watts input, a lower PF increases apparent power and current. For VA input, current is already determined by VA and voltage while PF converts VA to real watts.
  5. Use the result as an equipment-load conversion - This is not a dwelling/service demand-factor calculator and does not apply NEC Article 220 demand methods for you.
Quick answer

Add the loads first, then convert the combined power to current. Six input rows are available, but you only need to fill the loads that can operate together. Four example loads of 300 W, 600 W, 1,200 W, and 900 W total 3,000 W. At 120 V single-phase and power factor 1.00, that is 25 A and 3.0 kVA. At lower power factor, the same 3.0 kW requires more apparent power and therefore more current. This page performs that equipment-load conversion; it does not apply dwelling/service demand factors or decide the final breaker for you.

Combine Loads, Then Convert to Current

300 W600 W1,200 W900 WTotal 3,000 W25 A120 V, 1φ, PF 1.0
The calculator sums the positive load entries first, then converts the combined power to current. Two extra rows are available when a four-item list is not enough.

What Kind of Electrical Load Does This Calculate?

This is an equipment-load aggregation and power-conversion tool, not a dwelling service-load calculator. Enter several known watt or VA values, choose system voltage and phase, and CalcShed returns the combined current, real power, and apparent power.

It is intentionally different from a formal residential service-load calculation. NEC Article 220 demand factors, appliance rules, EV loads, cooking equipment, HVAC treatment, optional dwelling methods, and other service/feeder rules require a separate code workflow. This calculator does not hide those decisions behind a single “house size” field.

For a single resistive load where you only need a quick watts/amps/volts conversion, use the Watts Amps Volts Calculator. Use this page when you want to combine several known loads or include power factor and three-phase current.

Example Equipment Load List

ItemPowerRunning total
Lighting300 W300 W
Refrigeration equipment600 W900 W
Microwave / process load1,200 W2,100 W
Small appliance / auxiliary load900 W3,000 W

Illustrative values only. Use actual nameplate or measured power for the equipment being evaluated, and treat starting/inrush requirements separately.

Power and Current Formulas

The calculation keeps real power and apparent power separate:

Power factor = PF = real power (kW) ÷ apparent power (kVA)
Single-phase current = I = VA ÷ V
Balanced three-phase current = I = VA ÷ (√3 × V_LL)
Watts input = VA = W ÷ PF
VA input = W = VA × PF

For watts input, power factor affects the current because the supply must deliver the corresponding apparent power. For VA input, current comes directly from VA and system voltage; PF only tells you how much of that apparent power is real power.

Technical Sources

Next Steps

After converting the equipment load to current:

  1. Screen an OCPD planning sizeUse the current as an input, then verify equipment-specific and conductor rules.
  2. Size the conductorCheck usable ampacity and optionally voltage drop over distance.
  3. Plan backup powerIf these are outage loads, include running and starting demand in the generator workflow.

Related Calculators

Transformer CalculatorTranslate the load into transformer kVA and primary or secondary current.Power Factor CalculatorEvaluate kW, kVA, kVAR, and aggregate power factor when AC load quality matters.kVA to Amps CalculatorConvert known apparent power to current on single-phase or three-phase systems.Voltage Drop CalculatorCheck voltage drop after the operating current and conductor are known.

Load conversion is the starting point, not the entire circuit design. Browse the electrical calculator collection.

FAQ

Can I leave power factor blank?
Yes. A blank value is treated as 1.00. That is exact for a unity-power-factor assumption, not a claim that every motor, drive, power supply, or mixed load actually operates at PF 1. Use a measured or nameplate value when available.
Why does lower power factor increase amps when I enter watts?
Because the same real power requires more apparent power as PF falls. Since current is based on apparent power and voltage, the calculated current increases.
Is this a whole-house NEC load calculation?
No. It sums known W or VA values and converts the total to current. It does not apply Article 220 demand factors, optional dwelling methods, appliance-specific rules, or local service-sizing requirements.
What does the three-phase option assume?
It assumes a balanced three-phase load and uses line-to-line voltage in the standard √3 relationship. Unbalanced systems and detailed phase-by-phase load studies require a different calculation.
Updated Aug 2026 · See our Methodology
Equipment-load conversion only. This calculator does not perform a formal dwelling, service, feeder, demand-factor, fault-current, motor-starting, or equipment-specific code calculation. Use actual equipment data where available and verify final circuit/service design with the locally adopted code and a qualified electrical professional.