🔌 Watts to Amps Calculator
Convert watts to amps and amps to watts for DC, AC single-phase and three-phase circuits, with power factor, kVA and a common-voltage table.
Power factor is 1 for heaters, kettles and incandescent lights; motors, compressors and many power supplies are lower — the nameplate often lists it.
1,500 W ÷ (1 × 120 V) · apparent power 1.5 kVA
For a continuous load (3 hours or more), 12.5 A fits within 80% of a 20 A circuit. Wire size, breaker and local code must be confirmed by a licensed electrician.
Amps at common voltages (PF 1)
| Watts | 120 V | 230 V | 240 V | 277 V |
|---|---|---|---|---|
| 100 W | 0.83 | 0.43 | 0.42 | 0.36 |
| 500 W | 4.17 | 2.17 | 2.08 | 1.81 |
| 1,000 W | 8.33 | 4.35 | 4.17 | 3.61 |
| 1,500 W | 12.5 | 6.52 | 6.25 | 5.42 |
| 2,000 W | 16.67 | 8.7 | 8.33 | 7.22 |
| 3,000 W | 25 | 13.04 | 12.5 | 10.83 |
| 5,000 W | 41.67 | 21.74 | 20.83 | 18.05 |
What Watts to Amps Calculator Does
This watts to amps calculator converts power to current — and current back to power — for DC circuits, AC single-phase circuits such as household outlets, and AC three-phase systems used for motors and commercial buildings. Enter the voltage, and for AC the power factor, and the calculator shows the result with the formula filled in, the apparent power in kVA, and a table of amps at common voltages.
For household planning it also compares the current with common circuit sizes using the widely used rule of keeping continuous loads to 80% of a circuit’s rating. That is a guide for understanding loads — wiring, breaker sizing and code compliance must be confirmed by a licensed electrician.
How to Use Watts to Amps Calculator
- Choose watts → amps or amps → watts
- Pick DC, AC single phase or AC three phase
- Enter the power or current and the voltage
- Set the power factor for AC loads (1 for heaters)
- Read the result, kVA and the circuit guidance
Formula Used by Watts to Amps Calculator
Watts to amps
DC: I = P ÷ V · AC single phase: I = P ÷ (PF × V) · AC three phase: I = P ÷ (√3 × PF × V_LL)
Worked example
A 1,500 W space heater on 120 V (PF 1).
- 1,500 ÷ 120
Result: 12.5 A.
Three-phase
I = P ÷ (1.732 × PF × V_LL)
Worked example
A 10 kW motor load at 480 V, PF 0.9.
- 1.732 × 0.9 × 480 = 748.2
- 10,000 ÷ 748.2
Result: 13.4 A per line.
Circuit Capacity at 120 V
| Circuit | Full rating | 80% for continuous loads |
|---|---|---|
| 15 A | 1,800 W | 1,440 W |
| 20 A | 2,400 W | 1,920 W |
| 30 A | 3,600 W | 2,880 W |
How to Read Your Result
Why power factor matters
Motors, compressors and switching power supplies draw current that is partly out of step with the voltage. The meter bills for watts, but wires and breakers have to carry the full current, so a 1,000 W motor with power factor 0.8 draws as much current as a 1,250 W heater.
Low voltage means high current
The same power at lower voltage needs proportionally more current: 1,000 W is about 8.3 A at 120 V but 83 A at 12 V. That is why car and solar systems use thick cables and why inverters list their input current.
Limitations & Accuracy Notes
- Assumes steady loads; motors draw several times their running current when starting.
- Three-phase formulas assume a balanced load and line-to-line voltage.
- Not a substitute for an electrician’s load calculation or local electrical code.