Watts to Amps Calculator
Current from power and volts — Ohm’s law V = IR is the other page. Click any i for detail.
Load
Watts
i
Watts
Real power in watts. A 1,500 W heater is a common example. |
|
|---|---|
Volts
i
Volts
Circuit voltage. 120 V typical branch; 240 V for many dryers and ranges. |
|
Power factor
i
PF
1.0 for DC or a resistive heater. Motors are often 0.7–0.9. Three-phase power is a separate page. |
How to use this calculator
- Enter watts.
- Enter circuit volts.
- Leave PF at 1 for heaters; lower it for motors.
- Compare to breaker rating with a licensed electrician — this is I = P/(V×PF) only.
Results explained
Amps = watts ÷ (volts × power factor). Ohm’s law solves V, I, or R when you already have two of those. kWh from a device is the kWh calculator.
Quick reference: watts → amps
1,500 W on 120 V at PF 1 is 12.5 A.
| Item | Detail |
|---|---|
| 120 V × 12.5 A | 1,500 W at PF 1 |
| 240 V same watts | Half the amps |
| Ohm’s law | V = I R |
| Three-phase | Three-phase power calculator |
Nameplate FLA on a motor is not this DC-style division if PF and efficiency differ.
How the estimate is built
I = P / (V × PF).
Example scenario
1,500 W, 120 V, PF 1 → 12.5 A.
FAQ
Breaker size?
Not this page. Ampacity and continuous-load rules are code.
kW instead of W?
Multiply kW by 1,000 first.
Three-phase?
Use the three-phase power calculator.