Amps to Watts Calculator
Amps alone do not determine watts. Enter current, voltage, electrical system and power factor to estimate real power; use nameplate requirements for circuit design.
Quick answerAt 120 V and power factor 1, 10 A equals 1,200 W (1.2 kW) for DC or single-phase AC. At 230 V it equals 2,300 W. A balanced 400 V three-phase load at 10 A and power factor 0.8 is about 5,543 W.
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For the selected single- or balanced three-phase relationship.
Check current, voltage and real power with compatible equipment
Electrical access and equipment ratings determine what can be measured safely. The calculator remains an estimate; nameplates and installation requirements control circuit decisions.
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Amazon opens in a new tab. Measurement around energized equipment requires the correct category/range, intact leads and meter, safe access, training and PPE. Never open a panel solely to obtain a calculator input.
How it works
For DC or single-phase AC, real watts = amps × volts × power factor. For a balanced three-phase load, real watts = √3 × line current × line-to-line volts × power factor. Apparent VA uses the same relationship before multiplying by power factor. Kilowatts = watts ÷ 1,000. The calculator does not model harmonics, imbalance, startup or circuit-sizing rules.
Amps to watts examples
The DC/single-phase rows use power factor 1. The three-phase rows use line-to-line voltage and the stated power factor.
| Current and system | Voltage | Power factor | Real power |
|---|---|---|---|
| 10 A DC | 12 V | 1.00 | 120 W |
| 10 A single-phase | 120 V | 1.00 | 1,200 W |
| 10 A single-phase | 230 V | 1.00 | 2,300 W |
| 10 A single-phase | 230 V | 0.80 | 1,840 W |
| 10 A balanced 3-phase | 400 V L-L | 0.80 | 5,542.56 W |
| 20 A balanced 3-phase | 208 V L-L | 0.90 | 6,484.80 W |
Formula results are not conductor, breaker, inverter, generator or equipment sizing instructions. Follow the nameplate, manufacturer instructions and applicable electrical code.
Worked example: 10 A at 120 V
For DC or single-phase with power factor 1, 10 A × 120 V × 1 = 1,200 W, or 1.2 kW. With power factor 0.8, the same current and voltage correspond to 960 W of real power and 1,200 VA of apparent power.
Power factor therefore changes real watts without changing the entered RMS voltage and current. Do not assume an arbitrary 0.8 value for every motor or electronic device; use product data or suitable measurement.
Balanced three-phase needs the √3 factor
For a balanced three-phase load using line current and line-to-line voltage, real power = √3 × A × V × power factor. At 10 A, 400 V and PF 0.8, that is about 5,542.56 W.
If you have line-to-neutral voltage, per-phase values or an unbalanced system, do not mix them with this shortcut. Schneider Electric’s meter documentation shows the related phase-sum calculation; unusual systems need phase-by-phase data.
Real watts and apparent volt-amperes are different
Volts × amps gives apparent power for the selected DC/single-phase relationship; AC real power also depends on power factor. Utilities generally bill residential energy in kWh, while some tariffs or equipment ratings may also consider apparent power or demand.
To estimate energy, multiply real kW by representative operating hours. Current and power factor can change during a motor start, variable-speed cycle or electronic load, so one reading may not describe the whole period.
Do not use the result to size electrical equipment
Circuit design can depend on nameplate current, minimum circuit ampacity, maximum overcurrent protection, continuous-load treatment, duty cycle, conductor conditions, harmonics, imbalance and startup current. This arithmetic estimate cannot replace those requirements.
Use suitable equipment and qualified procedures for measurement. Do not open a panel or expose conductors solely to obtain an input for this calculator.
Sources used for assumptions: Schneider Electric — single-phase and balanced three-phase power calculations; U.S. Energy Information Administration — electricity glossary for watts, current and real power; Klein Tools — true-RMS clamp-meter specifications and measurement limits.
Frequently asked questions
How many watts is 10 amps?
At 120 V and power factor 1, 10 A is 1,200 W. At 230 V it is 2,300 W. Voltage, power factor and electrical system are required.
Can amps be converted to watts without voltage?
No. Current alone is not enough; at minimum you need voltage, and AC real power may also require power factor and phase/system information.
What power factor should I use?
Use 1 for DC or an appropriate purely resistive case. For other AC loads, use documented or suitably measured power factor instead of guessing a universal value.
Does the calculator support three-phase power?
Yes, for a balanced load using line current, line-to-line voltage and per-line power factor. Unbalanced systems require phase-by-phase calculation or measurement.
What is the difference between W and VA?
VA is apparent power from voltage and current; real watts include the power-factor adjustment for AC. At power factor 1 they have the same numeric value.
How do I turn watts into energy cost?
Divide real watts by 1,000 to get kW, multiply by representative hours to get kWh, then multiply by the applicable electricity rate.
Can I size a breaker or wire from this result?
No. Use the equipment nameplate and manufacturer requirements, applicable electrical code and qualified design. Startup, continuous-load and installation conditions are excluded.
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