Amps to watts calculator
Enter the current in amps and see the power in watts. Choose DC, single-phase AC or three-phase; if you leave the voltage empty we use 230 V, or 400 V for three-phase.
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's worked out
How it works
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Enter the values
Type the numbers or the formula. Decimals may use a point or a comma. No idea? Click Fill in an example.
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Instant answer
The answer appears as you type, with the most important intermediate values.
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See the working
Under "How it's worked out" you see the steps, handy for checking your own calculation.
How to convert amps to watts
Power is voltage times current:
- DC: P = U × I
- Single-phase AC: P = U × I × cos φ
- Three-phase AC: P = √3 × U × I × cos φ, where U is the voltage between two phases (400 V)
A 16 A circuit on 230 V delivers 230 × 16 = 3680 W. On a 120 V supply the same 16 A is 1920 W: type 120 in the voltage field.
Amps and watts for a connection
| Breaker | Single phase, 230 V | Three phase, 400 V |
|---|---|---|
| 10 A | 2300 W | 6928 W |
| 16 A | 3680 W | 11,085 W |
| 25 A | 5750 W | 17,321 W |
| 32 A | 7360 W | 22,170 W |
Values at cos φ = 1. This is why an electric car charges at about 3.7 kW from a single-phase 16 A supply, and at about 11 kW from a three-phase 16 A supply.
Working out the voltage
Choose Volts to find the voltage when you know the power and the current, for example for an adapter or a battery. For DC, such as a 12 V charger, choose DC: the power factor plays no part.
A word of caution
The result is the power that goes with this current. A circuit shouldn't simply be loaded to the full breaker rating all the time; leave changes to your installation to a qualified electrician.
Need the other direction? Use watts to amps. For batteries and power banks there is mAh to Wh.
Everyday values
| Supply | Current | Power |
|---|---|---|
| UK plug, 230 V | 13 A | 2990 W |
| US outlet, 120 V | 15 A | 1800 W |
| US outlet, 120 V | 20 A | 2400 W |
| Car outlet, 12 V | 10 A | 120 W |
| Phone charger, 5 V | 2 A | 10 W |
With a power factor
A motor draws 5 A on 230 V with cos φ = 0.85. The real power is 230 × 5 × 0.85 = 977.5 W. At cos φ = 1 it would have been 1150 W, which is the apparent power in volt-amperes.
From charge to energy
For batteries, current times time gives charge, and charge times voltage gives energy. The mAh to Wh converter works out that step, and the electricity cost calculator turns the power into a bill.
Frequently asked questions
How many watts is 13 amps?
On a 230 V supply, 13 × 230 = 2990 W, about 3 kW. That is the rating of a standard UK plug fuse, which is why many appliances there are limited to 3 kW.
What is the difference between watts and volt-amperes?
Watts are the useful power, and volt-amperes (VA) are voltage times current. They are equal when the power factor is 1. For motors and electronics, watts are lower, as explained in the [kW to kVA calculator](/en/math/kw-to-kva-calculator).
How do I find the voltage if I know watts and amps?
Choose *Volts* and enter the power and the current. 60 W at 5 A is 12 V.
Why does a three-phase 16 A connection give 11 kW and a single-phase one only 3.7 kW?
Three phases each carry 16 A, and √3 × 400 V × 16 A ≈ 11,085 W. A single phase at 230 V gives 230 × 16 = 3680 W.