Watts to Amps Calculator
Convert watts to amps, or amps to watts, for DC, single-phase or three-phase AC, with power factor. Shows the working.
See the full Watts to Amps Chart
New: please check your results.
For guidance only. This is not a substitute for a qualified engineer, and important designs should be checked by one.
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- Current
- 13.04 A
- Apparent power
- 3,000 VA
What it does
Convert an appliance's power in watts to the current it draws in amps, or the other way round. Choose the supply: single-phase AC for homes, three-phase AC for larger machines, or DC for batteries and vehicles. For AC, the power factor allows for motors and other loads that draw more current than their wattage suggests.
How to use it
- Convert
Which way to convert.
- Supply
Homes in the UK, Europe and the US are single-phase. Three-phase is for larger motors, workshops and commercial buildings. DC is for batteries, solar panels and vehicles.
- Power
The appliance's rating, usually on its plate or label: a kettle is about 3,000 W (3 kW). You can switch to kW or hp.
- Current
The current in amps.
- Voltage
230 V in the UK and Europe, 120 V in the US and Canada.
- Line-to-line voltage
The voltage between two phases: 400 V in the UK and Europe; 208 V or 480 V in the US.
- Voltage
For example 12 V or 24 V for vehicles and leisure batteries, 48 V for some solar systems.
- Power factor
1 for heaters, kettles, ovens and filament bulbs. About 0.8 to 0.9 for motors, pumps and compressors; check the rating plate ("cos φ").
Common uses
- Checking whether an appliance will run on a 13 A plug or a 16 A socket.
- Sizing a fuse, circuit breaker or inverter.
- Working out what a motor or heater draws on three-phase.
- Checking the voltage drop on the cable. Try the Cable Voltage Drop Calculator
- Working out volts, amps or ohms from the other two. Try the Ohm's Law Calculator
The formula
DC: I = P ÷ VSingle-phase AC: I = P ÷ (V × PF)Three-phase AC: I = P ÷ (√3 × V × PF)Apparent power (VA) = P ÷ PFWhere:
- I
- current in amps
- P
- real power in watts
- V
- voltage (line-to-line for three-phase)
- PF
- power factor, from 0 to 1
- √3
- about 1.732
Amps to watts uses the same formulas the other way round: P = V × I × PF (× √3 for three-phase).
Worked example
A 3,000 W appliance on a 230 V single-phase supply with a power factor of 1:
- Current: 3,000 W ÷ (230 V × 1) = 13.04 A
Questions people ask
How many amps is 3 kW?
On a 230 V single-phase supply, 3,000 W ÷ 230 V = about 13 A. That's why a 3 kW kettle is close to the limit of a 13 A plug. On 120 V it's 25 A.
What is power factor?
The share of the current that does useful work. Heaters and kettles use it all (power factor 1). Motors and some electronics draw extra current that flows back and forth, so for the same watts they need more amps. The rating plate often shows it as "cos φ".
Should I size a fuse or cable from this?
Use it as a starting point. Motors can draw several times their running current when starting, and cables and breakers have their own rules. For fixed wiring, ask a qualified electrician.
Last checked 2 November 2026 · Last rev. 31 October 2026 · 2ce0