Amps to Watts Calculator

Convert amps to watts for DC, single-phase or three-phase AC at any voltage and power factor, with kVA and the same current at other voltages.

Watts are volts times amps. A 15 A circuit at 120 V can supply up to 1,800 W, a 13 A UK plug at 230 V up to 2,990 W, and a 10 A Australian outlet 2,300 W at 230 V. For AC loads that aren't purely resistive, multiply by the power factor as well, and for three-phase multiply by √3. This calculator converts amps to watts and kilowatts for DC, single-phase AC and three-phase AC at any voltage and power factor. It also shows the apparent power in volt-amps (VA), and what the same current delivers at 12, 24, 48, 120, 208, 230, 240 and 400 V.

Mains
A
V
Power
1,200 W

1.2 kW

Current
10 A

at 120 V

Apparent power
1,200 VA

1.2 kVA

How it was worked out
  1. Single-phase AC: P = V × I × PF
  2. 120 V × 10 A × 1 = 1,200 W
Voltage10 A delivers
12 V120 W
24 V240 W
48 V480 W
120 V1,200 W
208 V2,080 W
230 V2,300 W
240 V2,400 W
400 V4,000 W
480 V4,800 W

Power factor is 1 for heaters, kettles and incandescent bulbs, and lower (often 0.8 to 0.95) for motors, compressors and some power supplies; the label or manual may give it. Three-phase uses the voltage between lines (208 or 480 V in the US, 400 V in the UK and Australia). Appliance labels usually give the most power drawn, so everyday current is often lower.

Common use cases

  • Find the most power a circuit, plug or extension lead can supply
  • Turn a clamp meter reading into watts
  • Work out the power of a motor or heater from its rated current
  • Size a generator or inverter from the current your loads draw

How to use

  1. Leave the converter on amps to watts, or switch to watts to amps.
  2. Pick DC, single-phase AC or three-phase AC. The voltage fills in for your country, and you can change it.
  3. Enter the current in amps.
  4. For AC, enter the power factor: 1 for heaters and kettles, lower for motors.
  5. Read the power in watts and kW, and the same current at other voltages in the table.

FAQ

How many watts is 13 amps?

2,990 W at 230 V and 3,120 W at 240 V. That's why UK plugs, fused at 13 A, suit appliances up to about 3 kW.

How many watts is 20 amps?

2,400 W at 120 V, 4,600 W at 230 V and 4,800 W at 240 V, for a load with a power factor of 1.

What's the difference between watts and volt-amps?

Volt-amps (VA) are simply volts × amps, the apparent power. Watts are the real power that does work: VA × power factor. They're equal for heaters and kettles, but a motor drawing 1,000 VA at a power factor of 0.8 uses 800 W. Generators, transformers and UPS units are often rated in VA or kVA.

How do I convert amps to watts on three-phase?

Multiply √3 (1.732) by the line-to-line voltage, the current and the power factor. 16.04 A at 400 V with a power factor of 0.9 is 1.732 × 400 × 16.04 × 0.9 = 10,000 W.

Related tools

Results are worked out from the figures you enter, for information only. They are not electrical, engineering or professional advice. Mains electricity can kill and start fires. Check cable and circuit sizes against the wiring rules where you live (the NEC and local amendments in the US, BS 7671 in the UK, AS/NZS 3000 and 3008 in Australia and New Zealand), and use a licensed electrician where the law requires one.