About the Watts to Amps Calculator
To know whether a plug, extension lead or circuit can supply a device, you need its current in amps, but most appliances are labelled in watts. This calculator divides the power by the voltage, and for AC loads it also divides by the power factor, and by the square root of three for three-phase supplies. Enter the wattage printed on the appliance and the supply voltage, and you get the current it will draw. It is useful for heaters, kettles, power tools, pumps, inverters and chargers, and for comparing the load on different circuits.
Updated October 2026
How to use the Watts to Amps Calculator
- 1Choose DC, single-phase AC or three-phase AC.
- 2Enter the power in watts.
- 3Enter the supply voltage.
- 4For AC loads, enter the power factor, or leave 1 for heaters and bulbs.
- 5Read the current in amps.
Examples you can check
A 2,000 watt hair dryer on 120 volts takes 16.7 amps, which is more than a typical 15 amp circuit can carry for long. The same dryer on 230 volts takes 8.7 amps. A 5 kilowatt three-phase heater on 400 volts with a power factor of 1 draws about 7.2 amps per line.
Differences like these explain why appliance power limits differ between countries.
If you are planning to run several appliances from one circuit, add up the watts of everything that could be on at the same time and convert the total, rather than converting each one on its own and adding rounded amp figures. Remember to include start-up surges for fridges, pumps and tools with induction motors, which can briefly draw several times their running current. A small margin keeps breakers from tripping at awkward moments.
Quick reference at common voltages
- 100 W: 0.83 A at 120 V, 0.43 A at 230 V.
- 500 W: 4.2 A at 120 V, 2.2 A at 230 V.
- 1,000 W: 8.3 A at 120 V, 4.3 A at 230 V.
- 2,000 W: 16.7 A at 120 V, 8.7 A at 230 V.
- 3,000 W: 25 A at 120 V, 13 A at 230 V.
Keep going
Use the Amps to Watts Calculator in the other direction, the kW to Amps Calculator for larger loads, the Wire Gauge Calculator to choose a cable size and the Energy Cost Calculator to see what a load costs to run. The Battery Charge Time Calculator helps with 12 volt systems.
Features
- Works for DC, single-phase and three-phase
- Power factor included for AC
- Handles any wattage or voltage
- Clear message for zero voltage
- Helps you compare circuits
- Nothing leaves your browser
Frequently asked questions
How do I convert watts to amps?
Divide the watts by the volts. A 1,500 watt heater on a 230 volt supply draws 1,500 divided by 230, which is 6.5 amps. For AC motors, divide by the voltage and the power factor.
How many amps is 1,000 watts?
At 120 volts it is 8.33 amps, at 230 volts it is 4.35 amps and at 12 volts it is 83.3 amps. Lower voltage means much higher current for the same power, which is why low-voltage wiring needs thick cables.
Why does a motor draw more amps than the watt figure suggests?
Motors have a power factor below 1 and an efficiency below 100 percent. A motor rated 1 kilowatt output may draw 1.3 kilowatts or more from the supply, and the current rises further at lower power factors. Enter the power factor if you know it.
What if my appliance label shows VA rather than watts?
Divide the volt-amperes by the voltage to get amps directly, because VA already includes the power factor. The VA to Watts Calculator converts between the two if you need the real power.
Can I use this to pick a circuit breaker?
It tells you the running current. Breakers and cables are chosen with extra margin, often loading a circuit to no more than 80 percent of its rating for continuous use, and motors need allowance for starting current. Follow your local wiring regulations.
What is the difference between line and phase current?
In a three-phase system the line current is the current in each supply conductor. The calculator uses line values, so enter the voltage between two lines and you get the current in each line.