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Watts to amps calculator

Enter the power in watts and see straight away how many amps an appliance draws. Choose DC, single-phase AC or three-phase; if you leave the voltage empty we use 230 V, or 400 V for three-phase.

What do you want to know?
Type of current

In watts; 2.3 kW works too.

In amps.

In volts. Empty = 230 V (UK, Europe), or 400 V for three-phase. In the US it is 120 V.

Empty = 1 (heaters, lamps). Motors and power supplies: 0.8 to 0.95.

Fill in the fields; the answer appears here straight away.

How it works

  1. Enter the values

    Type the numbers or the formula. Decimals may use a point or a comma. No idea? Click Fill in an example.

  2. Instant answer

    The answer appears as you type, with the most important intermediate values.

  3. See the working

    Under "How it's worked out" you see the steps, handy for checking your own calculation.

How to convert watts to amps

Current follows from power and voltage:

  • DC: I = P ÷ U
  • Single-phase AC: I = P ÷ (U × cos φ)
  • Three-phase AC: I = P ÷ (√3 × U × cos φ), where U is the voltage between two phases (400 V)

A 2300 W kettle on 230 V draws 2300 ÷ 230 = 10 A. As a rule of thumb, 1000 W on 230 V is about 4.3 A. On a 120 V supply, as in the US, the same 1000 W is 8.3 A: type 120 in the voltage field.

Watts and amps at 230 V (single phase, cos φ = 1)

| Power | Current | |---|---| | 100 W | 0.43 A | | 500 W | 2.17 A | | 1000 W | 4.35 A | | 2000 W | 8.70 A | | 3000 W | 13.04 A | | 3680 W | 16 A |

So a 16 A circuit can deliver about 3680 W. If several appliances share one circuit, add up their power.

What is cos φ?

With AC, the current in motors, transformers and power supplies doesn't peak at exactly the same moment as the voltage. That lag is the power factor (cos φ). For heaters and incandescent bulbs it is 1; for motors it is often between 0.8 and 0.9. A lower power factor means more current for the same power. If you leave the field empty, we use 1.

Fuses and cables

The tool shows the next standard breaker size (6, 10, 13, 16, 20, 25, 32, 40, 50 or 63 A). Treat this as a guide: the right breaker and cable size also depend on cable length, how it is installed and the type of load. Leave changes to your installation to a qualified electrician.

Need the other direction? Use amps to watts. To see what an appliance costs to run, try the electricity cost calculator.

Frequently asked questions

Is the watts to amps free?

Yes. The watts to amps is completely free, with no account, sign-up or usage limit.

How accurate is the result?

The tool calculates with your browser's number precision. For important calculations, always double-check what you entered.

Does it work on my phone?

Yes. The tool works in any modern browser on a phone, tablet or computer.