Watts to Amps Converter
Watts to amps for DC, single phase AC and three phase AC. Power factor gets its own field instead of being assumed.
Enter numbers. Voltage must not be zero and power factor must be between 0.1 and 1.
Reference only. Circuit, breaker and conductor sizing must follow the electrical code that applies where you are, and should be verified by a qualified electrician. This page doesn't give wire gauge, breaker sizing or installation guidance, and a converted figure isn't a substitute for a load calculation.
The formulas
AC single phase: A = W ÷ (V × PF)
AC three phase: A = W ÷ (V × PF × √3)
Each formula divides, because you are working back from power to the current that produced it. These follow from the definition of the watt as one joule per second and of the ampere as an SI base unit, so they are exact relationships rather than rounded conversion factors. Unit definitions per the NIST Guide to the SI.
Power factor is the input most converters leave out, and leaving it out always understates the current. A 2,000 watt motor at a power factor of 0.85 draws about 19.6 amps at 120 V, not the 16.7 you get by dividing watts by volts. Undersizing a breaker on that difference is the practical consequence, which is why it is a visible field here rather than a hidden assumption.
Reference table
| Watts | 12 V | 120 V | 240 V |
|---|---|---|---|
| 100 W | 8.33 A | 0.83 A | 0.42 A |
| 500 W | 41.67 A | 4.17 A | 2.08 A |
| 1,000 W | 83.33 A | 8.33 A | 4.17 A |
| 1,200 W | 100.00 A | 10.00 A | 5.00 A |
| 1,500 W | 125.00 A | 12.50 A | 6.25 A |
| 2,000 W | 166.67 A | 16.67 A | 8.33 A |
| 3,000 W | 250.00 A | 25.00 A | 12.50 A |
| 5,000 W | 416.67 A | 41.67 A | 20.83 A |
| 8,000 W | 666.67 A | 66.67 A | 33.33 A |
Every figure above assumes a power factor of 1, so it is the floor. A real motor on the same wattage draws more current than the table shows, never less.
Why the wattage alone won't tell you the current
An appliance label gives you watts. A breaker is rated in amps. Those are different quantities, and the bridge between them is the supply voltage, which the label usually doesn't repeat.
A 1,500 watt heater draws 12.5 amps on a 120 volt circuit and 6.25 amps on a 240 volt one. Same appliance, same label, half the current. That is why this tool asks for voltage before it returns anything, rather than quietly assuming 120 V and handing an American answer to someone in Europe.
If the load is a motor rather than a heating element, the power factor matters too, and the current will be higher than watts divided by volts suggests. Switch the circuit type above to expose it.
Common questions
What is 1000 watts in amps?
At 120 V, 1000 watts is 8.33 amps. At 240 V it is 4.17 amps. Voltage has to be part of the question, since watts alone don't determine current.
How do I convert watts to amps at 240V?
Divide the watts by 240. For an AC load with a power factor below 1, divide by 240 multiplied by the power factor as well.
How many watts are in an amp?
There is no fixed answer. Watts equal amps multiplied by volts, so an amp at 12 V is 12 watts while an amp at 240 V is 240 watts.
Does power factor matter for household appliances?
For heaters, kettles and incandescent lighting, not much, since those are close to purely resistive. For motors, air conditioners and some electronics it does, and ignoring it will understate the current drawn.
Related converters and guides
Sources
- NIST Guide to the SI, Appendix B: Conversion Factors. National Institute of Standards and Technology. Source for every conversion factor on this page, and for which factors are exact rather than rounded.