Power & phase
Watts to Amps Calculator
Current equals real power divided by voltage for DC, with power factor and the square-root-of-three phase factor added for AC modes. Enter the voltage and phase relationship used by the load.
Convert watts to current for DC, single-phase AC, and three-phase AC with explicit power factor.
Calculated result
Calculated current
Calculating…
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Planning math only. Verify equipment specifications and installation requirements separately.
What this calculator returns
Check whether the equipment rating is input or output power and use its stated power factor.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
I = P/V (DC); I = P/(V × PF) (1φ); I = P/(√3 × VLL × PF) (3φ).
- P
- Real power, in watts or kilowatts.
- S
- Apparent power, in volt-amperes or kilovolt-amperes.
- V
- RMS voltage; line-to-line voltage in three-phase modes.
- I
- Line or circuit current, in amperes.
- PF
- Power factor, expressed as a ratio from greater than zero through one.
- Q
- Reactive power, in volt-amperes reactive.
P is real power, V is voltage, PF is power factor, and VLL is line-to-line voltage.
Worked example
| Input | Value |
|---|---|
| System type | Single-phase AC |
| Real power | 2400 W |
| Voltage | 120 V |
2,400 W at 120 V and PF 1 is 20 A in DC or single-phase AC.
Reference table
| Voltage | Amps at 1 kW | Amps at 5 kW | Watts at 10 A |
|---|---|---|---|
| 120 V | 8.33 A | 41.67 A | 1,200 W |
| 208 V | 4.81 A | 24.04 A | 2,080 W |
| 240 V | 4.17 A | 20.83 A | 2,400 W |
| 480 V | 2.08 A | 10.42 A | 4,800 W |
Frequently asked questions
How many amps is 1,500 watts at 120 volts?
At power factor 1, 1,500 watts divided by 120 volts is 12.5 amps in DC or single-phase AC.
Should three-phase voltage be line-to-line?
Yes. Three-phase mode uses line-to-line voltage with the square-root-of-three relationship.
Why does AC need power factor?
Real power can be lower than apparent power, so current depends on PF for many AC loads.
Assumptions and limitations
- No breaker or conductor recommendation.
- Balanced three-phase system assumed.
Method and sources
Review the electrical formulas, calculation methodology, and reference tables for the references most relevant to this calculation. The broader technical sources index records source scope and verification. Last reviewed .