Watts to amps calculator
A watt rating tells you power. Add the supply voltage to find the current in amps. For AC loads, include the power factor too.
I = P ÷ V
100 ÷ (12) = 8.33333 A
This is current at the voltage you entered. At the same power, a lower battery voltage means more current.
8.33333 amps.
This calculation does not select a breaker or certify wire ampacity. Starting surges and equipment ratings need a separate check.
Watts to amps chart
DC values, or single-phase AC at power factor 1. These fixed reference values do not change with the calculator inputs.
| Power | 12 V | 24 V | 48 V | 120 V | 230 V |
|---|---|---|---|---|---|
| 100 W | 8.33333 A | 4.16667 A | 2.08333 A | 0.833333 A | 0.434783 A |
| 500 W | 41.6667 A | 20.8333 A | 10.4167 A | 4.16667 A | 2.17391 A |
| 1000 W | 83.3333 A | 41.6667 A | 20.8333 A | 8.33333 A | 4.34783 A |
| 2000 W | 166.667 A | 83.3333 A | 41.6667 A | 16.6667 A | 8.69565 A |
How to convert watts to amps
For DC, divide watts by volts. A 100 W load on a 12 V supply draws about 8.33 A. The same 100 W load on a 24 V supply draws about 4.17 A.
Single-phase AC: A = W ÷ (V × PF)
Balanced three-phase AC, line to line: A = W ÷ (√3 × V × PF)
Balanced three-phase AC, line to neutral: A = W ÷ (3 × V × PF)
AC formulas use RMS voltage and current. For example, 1,000 W at 120 V and a power factor of 0.8 draws about 10.42 A. Dividing by voltage alone would underestimate that current.
Calculation references
See OpenStax on AC power for RMS values and power factor, and Schneider Electric’s Electrical Installation Guide for single-phase and three-phase current relationships.
Using a power rating
How many amps is 1,000 watts?
It depends on voltage and circuit type. At 12 V DC, 1,000 W is about 83.33 A. At 120 V single-phase AC with a power factor of 1, it is about 8.33 A.
Can I use this for a battery and inverter?
Use the DC mode for current drawn from the battery. First divide the AC load’s real watts by the inverter efficiency as a decimal, then enter that DC input power and the battery voltage. For example, a 900 W load at 90% efficiency needs 1,000 W from the battery, or about 83.33 A at 12 V. This simplified example excludes separate idle draw and starting surges.
Are watts and volt-amps the same?
Watts measure real power. Volt-amps measure apparent power. In AC circuits they are equal only at a power factor of 1. Enter watts here, not a VA rating.
How do I convert amps back to watts?
For DC, multiply amps by volts. For single-phase AC, also multiply by power factor. If you know current and resistance instead, use the Ohm’s law calculator.