Amps to Watts Calculator
Convert amps to watts, or watts to amps, for DC, single-phase AC and three-phase circuits. Enter the current or power, the voltage and the power factor, and get watts, kilowatts, amps and apparent power in volt-amps.
Amps to watts calculator
How to use the amps to watts calculator
- Choose the direction. Pick amps to watts, or watts to amps if you know the power and want the current.
- Choose the circuit. Use DC for batteries and solar, AC single-phase for ordinary sockets, and AC three-phase for industrial supplies with the line-to-line voltage.
- Enter the voltage. Type the supply voltage. Typical values are 120 V in the US and Canada, and 230 V in the UK and Australia. The default follows your region.
- Set the power factor. For heaters and incandescent lamps use 1. Motors and many power supplies are 0.8 to 0.95. Leave it at 1 for DC.
- Read the result. See watts and kilowatts, the current, and the apparent power in volt-amps. Check wire and breaker ratings before relying on any figure.
Amps to watts formulas
DC: W = V × A
AC single-phase: W = V × A × PF
AC three-phase: W = √3 × VLL × A × PF
Watts to amps: A = W ÷ (V × PF), or W ÷ (√3 × V × PF)
Watts measure real power, volts measure electrical pressure and amps measure current. Direct current is the simple case. In alternating current, current and voltage can peak at different moments, so the power factor (PF) scales the product. Three-phase power adds √3 (1.732) when you use the voltage measured between two lines.
Worked examples
A heater on 120 V. 10 A × 120 V × 1 = 1,200 W. In reverse, a 1,500 W heater draws 1,500 ÷ 120 = 12.5 A.
A UK appliance. A 13 A plug fuse on 230 V allows up to 13 × 230 = 2,990 W, about 3 kW.
A three-phase motor. 10 A on 400 V with a power factor of 0.8 is √3 × 400 × 10 × 0.8 = 5,542.56 W, or 5.54 kW.
DC and batteries. 20 A from a 12 V battery is 240 W, and 5 A at 48 V is 240 W as well.
Typical voltages
| Region or system | Typical voltage |
|---|---|
| United States and Canada, sockets | 120 V single-phase |
| United Kingdom, Australia, much of Europe | 230 V single-phase |
| US large appliances (dryer, range) | 240 V |
| Three-phase industrial (Europe, UK, Australia) | 400 V line-to-line |
| Three-phase commercial (US) | 208 V or 480 V line-to-line |
| Cars and RVs | 12 V DC |
Watts, kilowatts and volt-amps
A kilowatt is 1,000 watts. The apparent power in volt-amps is voltage times current without the power factor, so a 10 A motor on 230 V draws 2,300 VA even if its real power is 1,840 W at a power factor of 0.8. Utilities and generator ratings often use kVA, while appliances are labelled in watts. Energy, as on your bill, is power over time: a 2 kW heater for 3 hours uses 6 kWh.
Features
- Amps to watts and watts to amps in one tool.
- DC, single-phase AC and three-phase AC, with power factor.
- Defaults for 120 V or 230 V based on your region.
- Copy result, reset and a printable report in five themes on A4 or Letter.
Related converters and calculators
Convert engine and motor ratings with the horsepower to kW converter, or any other unit with the unit converter. For long cable runs, check the voltage drop calculator. It is not a substitute for a qualified electrician’s circuit design.
Frequently asked questions
How do you convert amps to watts?
Multiply amps by volts. For DC, 10 A at 12 V is 120 W. For single-phase AC, also multiply by the power factor: 10 A at 230 V and a power factor of 0.9 is 2,070 W.
Can you convert amps to watts without the voltage?
No. Watts depend on both current and voltage, so one amp can be 12 W on a car battery or 230 W on a UK socket. You must know the voltage.
What is the three-phase formula?
Watts = √3 × line-to-line volts × amps × power factor. With 400 V, 10 A and a power factor of 0.8, that is 5,543 W.
What is power factor?
It is the ratio of real power in watts to apparent power in volt-amps. A resistive heater has a power factor of 1, while motors and some electronics are lower because current and voltage are out of step.
What is the difference between watts and volt-amps?
Watts are real power that does useful work. Volt-amps (VA) are apparent power, voltage times current. They are equal only when the power factor is 1.
How many amps is 1,500 watts?
At 120 V, 1,500 W is 12.5 A. At 230 V it is 6.52 A, which is why the same heater draws less current in the UK.
Can I use this to size a circuit breaker?
No. It gives the load current only. Breaker and wire sizes depend on local electrical codes, continuous-load rules, cable length and temperature, so ask a qualified electrician.
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Sources and references
About this calculator
Written and maintained by Rashid Mehmood, founder of CalcTen. The formulas are unit-tested against hand-worked examples, and the content is reviewed whenever product sizes or guidance change. Last updated 14 November 2026. See our editorial policy.
Conversion factors come from NIST and other standards bodies, and results are rounded for display. For safety-critical work such as medicines, engineering or navigation, verify with an authoritative source. Read the disclaimer.