Watts to Amps Calculator
Convert between watts, amps, and volts for AC and DC circuits. Enter any two values to calculate the third.
Typical: 0.8–0.95 for motors; 1.0 for resistive loads
Watts
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W
Amps
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A
Volts
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V
Watts to Amps Formulas
DC and Single-Phase AC (Resistive Loads)
$$I = \frac{P}{V}$$
$$P = V \times I$$
Single-Phase AC with Power Factor
$$I = \frac{P}{V \times PF}$$
Three-Phase AC
$$I = \frac{P}{V \times \sqrt{3} \times PF} = \frac{P}{V \times 1.732 \times PF}$$
Quick Reference: Common Appliances
| Appliance | Watts | Amps at 120 V | Amps at 240 V |
|---|---|---|---|
| LED bulb | 10 W | 0.08 A | — |
| Phone charger | 20 W | 0.17 A | — |
| Laptop | 65 W | 0.54 A | — |
| Microwave | 1,000–1,500 W | 8.3–12.5 A | — |
| Window AC (5,000 BTU) | 550 W | 4.6 A | — |
| Electric kettle | 1,500 W | 12.5 A | — |
| Hair dryer | 1,875 W | 15.6 A | — |
| Electric dryer | 5,000 W | — | 20.8 A |
| Electric range | 8,000 W | — | 33.3 A |
| EV charger (Level 2) | 7,200 W | — | 30 A |
Why Voltage Matters
The same wattage draws very different currents at different voltages. A 1,000 W appliance draws 8.3 A at 120 V but only 4.2 A at 240 V. This is why high-power appliances (dryers, ranges, HVAC) use 240 V — the lower current means thinner wire can be used.
Frequently Asked Questions
How many amps is 1000 watts at 120 volts?
1,000 W ÷ 120 V = 8.33 amps. This is close to the limit of a standard 15 A outlet (rated at 80% continuous = 12 A). For a 1,000 W continuous load, use a 20 A circuit.
How many watts can a 15 amp circuit handle?
A 15 A circuit at 120 V has a maximum of 15 × 120 = 1,800 W. However, the NEC limits continuous loads to 80% of the breaker rating, so the practical maximum for continuous use is 15 × 0.8 × 120 = 1,440 W.
What is the difference between watts and volt-amps (VA)?
Watts (W) is real power — the actual work done. Volt-amps (VA) is apparent power — the product of RMS voltage and current. They are equal for resistive loads (heaters, incandescent bulbs) but differ for reactive loads (motors, computers). The ratio W/VA is the power factor.
