Amps to watts
Power in watts is current times voltage: P = I × V. A 15 A circuit at 120 V can carry 1 800 W; at 230 V the same 15 A carries 3 450 W.
Amps to watts 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
P (W) = I × V × PF
Step by step
- Multiply: 15 A × 120 V = 1,800 W.
Amps to watts table
| Amps | 12 V | 120 V | 230 V | 240 V |
|---|---|---|---|---|
| 1 A | 12 W | 120 W | 230 W | 240 W |
| 5 A | 60 W | 600 W | 1,150 W | 1,200 W |
| 10 A | 120 W | 1,200 W | 2,300 W | 2,400 W |
| 15 A | 180 W | 1,800 W | 3,450 W | 3,600 W |
| 20 A | 240 W | 2,400 W | 4,600 W | 4,800 W |
| 30 A | 360 W | 3,600 W | 6,900 W | 7,200 W |
| 32 A | 384 W | 3,840 W | 7,360 W | 7,680 W |
| 40 A | 480 W | 4,800 W | 9,200 W | 9,600 W |
| 50 A | 600 W | 6,000 W | 11,500 W | 12,000 W |
| 100 A | 1,200 W | 12,000 W | 23,000 W | 24,000 W |
Table uses the circuit type and power factor set under Options (AC single-phase, PF 1).
FAQ
Choose a voltage preset or type your own. Options holds the power factor and three-phase settings.
How do I convert amps to watts?
Multiply the amps by the volts: watts = amps × volts. For AC loads, multiply by the power factor as well.
How many watts is 15 amps?
15 A is 1 800 W at 120 V, 3 450 W at 230 V and 180 W 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.