Calculators · Electrical converters
Watts, amps, volts — and how to convert between them
It all comes down to one relationship: watts = volts × amps. Know any two and you can find the third. These converters do the math in your browser, default to the right US voltage, and — unlike a bare calculator — tell you the part you actually care about: whether it'll trip your breaker.
The one formula
Watts = Volts × Amps. So Amps = Watts ÷ Volts and Volts = Watts ÷ Amps. For a motor or AC unit, multiply by the power factor (~0.8) — they pull a little extra. And remember watts is power, while kWh is energy over time (watts × hours ÷ 1,000) — that's the one your bill counts.
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Common questions
- How are watts, amps, and volts related?
- Watts = volts × amps. Rearrange it and you can find any one from the other two: amps = watts ÷ volts, volts = watts ÷ amps. That single relationship powers every converter here.
- Why do I need voltage to convert watts to amps?
- Because amps = watts ÷ volts — without the voltage there are two unknowns. The same wattage draws half the amps at 240V as it does at 120V, so voltage changes the answer.
- What's the difference between watts and kWh?
- Watts is power (the rate you're using energy right now); a kilowatt-hour is energy (power × time) — and it's what your utility bills. kWh = watts × hours ÷ 1,000.
Trying to lower the bill behind all these numbers?