How to convert watts to amps (the formula)
Amps come from power and voltage. Watts is power, so the current is watts divided by the voltage — and, on AC, divided by the power factor too. Three cases:
| System | Formula | Example |
|---|---|---|
| DC | I = W ÷ V | 1500 W ÷ 120 V = 12.5 A |
| AC single-phase | I = W ÷ (V × PF) | 1500 W, 120 V, PF 1 = 12.5 A |
| AC three-phase | I = W ÷ (√3 × V × PF) | 10,000 W, 480 V, PF 1 = 12.03 A |
The √3 (about 1.732) in the three-phase formula comes from three-phase geometry — the same wattage draws fewer amps per line on three-phase. If your power is in kilowatts, multiply by 1000 first (or use the kW to amps calculator).
How many amps is X watts?
The common wattages converted to amps at power factor 1.0 (single-phase) — divide by your power factor for a motor load:
| Power | 120 V | 240 V |
|---|---|---|
| 500 W | 4.17 A | 2.08 A |
| 1000 W | 8.33 A | 4.17 A |
| 1500 W | 12.5 A | 6.25 A |
| 2000 W | 16.67 A | 8.33 A |
| 3000 W | 25 A | 12.5 A |
| 5000 W | 41.67 A | 20.83 A |
| 7000 W | 58.33 A | 29.17 A |
A quick sense check: 1000 watts is about 8.3 amps at 120 V and half that (4.17 A) at 240 V — doubling the voltage halves the current for the same power, which is why heavy loads run at 240 V.
Common appliances (and the 80% rule)
Most "how many amps is X watts" questions come from a specific device on a 120-volt outlet. Here's where the everyday ones land:
| Appliance (120 V) | Watts | Amps |
|---|---|---|
| Coffee maker | 1000 W | 8.3 A |
| Microwave | 1200 W | 10 A |
| Space heater | 1500 W | 12.5 A |
| Hair dryer | 1875 W | 15.6 A |
A breaker should only carry 80% of its rating on a continuous load — so a 15 A circuit tops out at 12 A, and a 20 A circuit at 16 A. That's why a 1500 W space heater (12.5 A) should be the only thing on a 15 A circuit, and a 1875 W hair dryer (15.6 A) needs a 20 A circuit — which is exactly why bathroom and kitchen receptacles are 20 A.
Power factor and three-phase
On AC, the amps depend on power factor: since real watts = V × A × PF, solving for current means dividing by PF — so a lower power factor gives more amps for the same watts. Resistive loads (heaters, incandescent bulbs) are PF 1.0; motors run around 0.8.
1500 W at 120 V:
• at PF 1.0 (resistive) → 12.5 A
• at PF 0.8 (motor) → 15.63 A
And three-phase divides by an extra √3, so 10,000 W at 480 V is just 12.03 A per line.
Watts, kilowatts, and volts
These conversions all connect. 1 kW = 1000 W, so for a kilowatt rating use the kW to amps calculator. To go the other direction — volts and amps back to power — use volts to watts. And for motors, generators, and transformers rated in horsepower or kVA, see HP to amps and kVA to amps.
From amps to a circuit (size the wire and breaker)
Once you have the amps, size the breaker and wire — and remember the NEC 125% rule for continuous loads (running three hours or more): a 12.5 A continuous load is figured at about 15.6 A. Run your number through the Wire Size Calculator and the Breaker Size Calculator, and the AWG ampacity chart has the conductor ratings.
Frequently asked questions
ConversionsWhat is the formula to convert watts to amps?
ConversionsHow many amps is 1000 watts?
ConversionsHow many amps is 1500 watts?
ConversionsHow many amps is 5000 watts?
ConversionsHow do I convert watts to amps at 240V?
ConversionsDoes power factor change watts to amps?
ConversionsHow do I convert watts to amps for three-phase?
ConversionsHow many amps is 7000 watts?
This calculator gives estimates from the standard power formula. Real AC loads vary with power factor, and circuit sizing follows the NEC and your local authority having jurisdiction (AHJ). When in doubt, hire a licensed electrician.