Watts / Amps / Volts
Watts to Amps Calculator
Convert watts to amps, amps to watts, or watts to volts, with power factor for motor loads. The formula, a worked example, and a 120V and 240V chart.
Watts to Amps Chart (Resistive, PF 1.0)
| Watts | Amps at 120V | Amps at 240V |
|---|---|---|
| 500 W | 4.17 A | 2.08 A |
| 1,000 W | 8.33 A | 4.17 A |
| 1,200 W | 10 A | 5 A |
| 1,500 W | 12.5 A | 6.25 A |
| 1,800 W | 15 A | 7.5 A |
| 2,000 W | 16.67 A | 8.33 A |
| 3,000 W | 25 A | 12.5 A |
| 5,000 W | 41.67 A | 20.83 A |
Resistive loads at unity power factor. For a motor or other reactive load, divide by the power factor (about 0.8 to 0.9). Three-phase divides by an added 1.732.
Frequently Asked Questions
How many amps is 1500 watts?
1500 watts is 12.5 amps at 120 volts, and 6.25 amps at 240 volts. The formula is amps = watts / volts, so 1500 / 120 = 12.5. That assumes a resistive load with a power factor of 1.0, which is true for space heaters, toasters, and most 120V appliances. For a motor with a 0.85 power factor, 1500 W draws 1500 / (120 x 0.85) = 14.7 amps.
How do I convert watts to amps?
Divide the watts by the volts: amps = watts / volts. At 120V, 1000 watts is 8.33 amps; at 240V it is 4.17 amps. If the load is an AC motor or other reactive load, divide by the power factor as well: amps = watts / (volts x power factor). Three-phase power adds a 1.732 factor: amps = watts / (volts x 1.732 x power factor).
How do I convert amps to watts?
Multiply amps by volts: watts = volts x amps. A 20 amp, 120V circuit is 2400 watts. For a motor load, multiply by the power factor: watts = volts x amps x power factor. This is the real (working) power in watts; volts x amps alone gives apparent power in VA.
What is power factor and when does it matter?
Power factor is the ratio of real power (watts) to apparent power (volt-amps) in an AC circuit. Resistive loads such as heaters and incandescent bulbs have a power factor of 1.0, so watts and VA are equal. Motors, transformers, and many electronic loads are reactive, with a power factor around 0.8 to 0.9, which means they draw more current than watts alone suggest. Use the nameplate power factor when sizing conductors and breakers for motor loads.
How many amps does a 240V circuit draw?
At 240 volts, amps = watts / 240 (for a resistive load). A 5000 watt load is 20.8 amps, a 4500 watt water heater is 18.75 amps, and a 9600 watt range element bank is 40 amps. Doubling the voltage from 120V to 240V halves the current for the same wattage, which is why large appliances run on 240V: they move the same power with less current and smaller wire.