Watts to Amps Calculator
Convert watts to amps with this calculator. Enter power in watts and the voltage to find the current in amps, using the formula amps = watts divided by volts.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Watts to Amps Calculator Works
This calculator converts power in watts into current in amps using the supply voltage. Watts measure how much power a device uses, while amps measure how much current flows. They are linked by voltage through the power equation W = A × V.
The Formula
Amps = watts ÷ volts
Because power equals current multiplied by voltage, rearranging gives current as power divided by voltage. You must supply the voltage to get a meaningful amp value.
Worked Example
A 1,500 W space heater on a 120 V circuit:
- Amps = 1,500 ÷ 120 = 12.5 A
The same heater on a 240 V supply:
- Amps = 1,500 ÷ 240 = 6.25 A
This is why high-power appliances are often wired at higher voltage: the current, and therefore the wire size, is smaller.
Watts to Amps Quick Reference (at 120 V)
| Watts | Amps (120 V) |
|---|---|
| 500 | 4.17 |
| 1000 | 8.33 |
| 1500 | 12.5 |
| 1800 | 15.0 |
| 2400 | 20.0 |
AC, DC and Power Factor
For DC circuits and resistive AC loads (heaters, kettles, incandescent bulbs) the formula above is exact. For reactive AC loads such as motors and transformers, multiply the voltage by the power factor (often 0.8 to 0.95) before dividing, so amps = watts ÷ (volts × power factor).
Frequently asked questions
How do I convert watts to amps?+
Divide the power in watts by the voltage. For example, 1,500 watts at 120 volts is 1,500 ÷ 120 = 12.5 amps. You must know the voltage because watts alone do not determine current.
How many amps is 1500 watts?+
It depends on voltage. At 120 V, 1,500 W draws 12.5 amps. At 240 V, the same 1,500 W draws only 6.25 amps. Higher voltage means lower current for the same power.
Why do I need the voltage to convert watts to amps?+
Power equals current times voltage (W = A × V). Without knowing the voltage you cannot separate current from power, so the converter always asks for the supply voltage.
Does this work for AC and DC?+
It works directly for DC and for resistive AC loads with a power factor of 1, such as heaters and incandescent bulbs. For motors and other reactive loads, divide the result by the power factor as well.
What voltage should I use?+
Use the voltage of your supply: typically 120 V in North America, 230 V in Europe and the UK, or 12 V and 24 V for many vehicle and battery systems. Check the device label if unsure.