Watts to amps
Current in amps is power in watts divided by voltage: I = P ÷ V. A 1 500 W space heater on a 120 V outlet draws 12.5 A; the same heater on 230 V draws about 6.5 A.
Watts to amps calculator
AC single-phase, power factor 1 · change under Options
Resistive loads (heaters, kettles, incandescent bulbs) have power factor 1. Motors are often 0.8–0.9. For three-phase, enter the line-to-line voltage (for example 208, 400 or 480 V).
How it’s calculated
1 W = 1 V × 1 A · 1 kW = 1 000 W
I (A) = P (W) ÷ (V × PF)
Step by step
- Divide: 1,500 W ÷ 120 V = 12.5 A.
Watts to amps table
| W | 12 V | 120 V | 230 V | 240 V |
|---|---|---|---|---|
| 60 W | 5 A | 0.5 A | 0.26087 A | 0.25 A |
| 100 W | 8.3333 A | 0.83333 A | 0.43478 A | 0.41667 A |
| 500 W | 41.667 A | 4.1667 A | 2.1739 A | 2.0833 A |
| 1000 W | 83.333 A | 8.3333 A | 4.3478 A | 4.1667 A |
| 1500 W | 125 A | 12.5 A | 6.5217 A | 6.25 A |
| 2000 W | 166.67 A | 16.667 A | 8.6957 A | 8.3333 A |
| 3000 W | 250 A | 25 A | 13.043 A | 12.5 A |
| 5000 W | 416.67 A | 41.667 A | 21.739 A | 20.833 A |
Table uses the circuit type and power factor set under Options (AC single-phase, PF 1).
FAQ
Pick the voltage, or type your own. For motors and three-phase supplies, open Options to set the power factor and circuit type.
How do I convert watts to amps?
Divide the watts by the volts: amps = watts ÷ volts. For AC loads with a power factor below 1, divide by (volts × power factor) instead.
How many amps is 1000 watts?
1 000 W draws 8.33 A at 120 V, 4.35 A at 230 V and 83.3 A at 12 V (power factor 1).
What voltage should I use?
Use the voltage the device runs on: 120 V for standard North American outlets, 230 V in the UK, Europe and much of the world, 240 V for large North American appliances, and 12 V for car and RV electrics.
What is power factor?
Power factor (PF) is the share of AC current that does useful work. Resistive loads such as heaters and incandescent bulbs have PF 1. Motors and some power supplies are lower, often 0.8 to 0.95, which means they draw more amps for the same watts. Set it under Options.
What about three-phase power?
For a balanced three-phase load, I = P ÷ (√3 × V × PF), where V is the line-to-line voltage. Choose “AC three-phase” under Options.
Can I size a breaker or wire with this?
Unitglide gives the current the load draws. Breakers and wiring must follow your local electrical code, which adds safety margins (for example 80% continuous load rules), so check with a licensed electrician.
Sources
- NIST SP 811 and the SI Brochure (BIPM): 1 W = 1 V × 1 A: P = V × I for DC; P = V × I × PF for single-phase AC; P = √3 × V × I × PF for three-phase AC.
Checked by Unitglide on 2026-10-27.