Energy & Workshop Math
Amps to Watts Calculator
Convert load current in amps to real power in watts for DC, AC single-phase or balanced three-phase circuits.
Enter your measurements
Results update as you type.
About this calculator
Enter the current and the circuit voltage. For AC circuits the power factor is required — take it from the equipment nameplate. Three-phase mode assumes a balanced load and a line-to-line RMS voltage. This is the inverse of the watts-to-amps calculator and uses the same stated mathematical model.
How to measure
- Use current and voltage for the selected circuit model.
- For three phase, enter line current and line-to-line voltage.
- Enter power factor for AC real power; the output is not apparent VA or mechanical horsepower.
How to use this calculator
- Choose the circuit type.
- Enter the measured or rated current.
- Enter the circuit voltage — line-to-line for three phase.
- For AC, enter the nameplate power factor.
- Calculate for real power in watts and kilowatts.
Formula
DC: power = current × voltage
AC single phase: power = current × voltage × power factor
AC three phase (balanced): power = √3 × current × line-to-line voltage × power factor
Assumptions
- Power is real (electrical) power, not apparent power.
- AC uses the stated RMS voltage and power-factor model.
- Three-phase loads are assumed balanced.
Common mistakes
- Assuming amps determine watts without voltage.
- Confusing real watts with apparent volt-amperes.
- Using an unbalanced load in a balanced three-phase approximation.
Worked example
Try it: press “Load example” above the form.
10 A at 230 V single phase with PF 0.8 is 10 × 230 × 0.8 = 1,840 W.
Limitations
No conductor or breaker sizing, code compliance, or unbalanced and harmonic analysis.
Frequently asked questions
Do amps alone tell me watts?
No. You also need voltage and, for AC real power, the power factor and circuit type. Balanced three-phase arithmetic uses line-to-line voltage.
Are watts and volt-amperes the same?
They are equal only for unity power factor in this model. Watts describe real power. Volt-amperes describe apparent power; reactive loads can make the two differ.
What does the worked example show?
10 A at 230 V single phase with PF 0.8 is 10 × 230 × 0.8 = 1,840 W.
Which assumptions should I check before using the result?
No conductor or breaker sizing, code compliance, or unbalanced and harmonic analysis.
Sources
Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.
- OpenStax: electrical power and energy
DC power and energy relationships. AC/runtime assumptions are stated separately and require appropriate domain review.
- ABB: electrical handbook
Voltage-drop mathematical context, section 2.2.2. Historical handbook, not current code authority or wire-sizing guidance.
- ABB: electrical installation handbook mathematical appendix
Historical manufacturer handbook: DC, single-phase and balanced-three-phase real-power/current relationships. Not current local-code approval.
Calculation documentation · Updated 2026-11-11 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.
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