How to use this watts to amps calculator
- Power, enter the load in watts (W).
- Voltage, enter the supply voltage in volts (V), for example 120 or 240.
- Current type, choose DC, AC single-phase or AC three-phase to match your circuit.
- Power factor, set it for AC loads (around 0.8 for motors, near 1.0 for heaters).
- Read the current in amps, it updates instantly as you type.
Nothing is submitted or stored: the numbers never leave your device, so you can size cables and breakers privately.
Watts to amps formula
Current is power divided by voltage, but AC circuits add the power factor (and for three-phase, the square root of three). The three cases this calculator uses are:
- DC: A = W / V
- AC single-phase: A = W / (V × PF)
- AC three-phase: A = W / (√3 × V × PF)
Here A is current in amps, W is real power in watts, V is voltage in volts and PF is the power factor. For three-phase, V is the line-to-line voltage and √3 is about 1.732. As an example, 1200 W on a DC 120 V supply gives 1200 / 120 = 10 A.
A note on power factor
Power factor describes how effectively a load turns supplied power into useful work, on a scale from 0 to 1. Purely resistive loads such as electric heaters, kettles and incandescent bulbs sit very close to 1.0, so for those you can leave the power factor at 1. Inductive loads like motors, pumps, compressors and transformers run lower, often 0.7 to 0.9, which is why 0.8 is a sensible default when the exact figure is unknown. A lower power factor means more current is needed for the same real power, so it matters when you are sizing conductors and protection.
Why convert watts to amps?
Cables, fuses and circuit breakers are rated in amps, not watts, so knowing the current draw is essential for choosing the right wire gauge and protection. It also helps you check whether a circuit or generator can handle a load, and lets you balance appliances across phases or batteries. Always treat the result as a guide and confirm against your local electrical code before wiring anything.
Safety note: This calculator is for general information only and is not professional electrical advice. Real-world current can be affected by efficiency, voltage drop and inrush. Consult a qualified electrician and follow your local code for any installation.
Frequently asked questions
How do you convert watts to amps?
For DC, divide power by voltage: amps = watts / volts. For AC, also divide by the power factor (and √3 for three-phase).
How many amps is 1000 watts at 120 volts?
On a DC or resistive 120 V supply, 1000 watts is about 8.33 amps. With an AC power factor of 0.8 it is about 10.42 amps.
What power factor should I use?
Use 1.0 for heaters and incandescent lamps, and roughly 0.7 to 0.9 for motors and electronics. 0.8 is a common default.
Is my data uploaded?
No, everything is calculated on your device and nothing is sent anywhere.