Watts to Amps Calculator
Convert watts to amperes for any voltage. Enter the power in watts and voltage to calculate current in amps. Works for 12V, 120V, and 240V circuits.
How to Convert Watts to Amps
The formula to convert watts to amps is: Amps = Watts ÷ Volts. This is derived from Ohm's Lawand the power equation P = V × I, rearranged to I = P / V, where P is power in watts, V is voltage in volts, and I is current in amperes.
Single-phase: A = W ÷ V
Three-phase: A = W ÷ (V × √3)
For example, a 1,500-watt space heater at 120 volts draws 12.5 amps (1,500 ÷ 120). The same 1,500 watts at 240 volts draws only 6.25 amps — which is why converting to higher voltage reduces current draw and allows smaller wire sizes.
Three-phase note:For three-phase circuits, the formula becomes Amps = Watts ÷ (Volts × √3). For example, 10,000 watts on a 480V three-phase system draws about 12.03 amps (10,000 ÷ (480 × 1.732) = 12.03). The √3 factor accounts for the phase relationship between the three conductors.
Watts to Amps Conversion Chart
| Watts | @ 12V | @ 120V | @ 240V |
|---|---|---|---|
| 100 W | 8.33 A | 0.83 A | 0.42 A |
| 200 W | 16.67 A | 1.67 A | 0.83 A |
| 500 W | 41.67 A | 4.17 A | 2.08 A |
| 750 W | 62.50 A | 6.25 A | 3.13 A |
| 1,000 W | 83.33 A | 8.33 A | 4.17 A |
| 1,500 W | 125.00 A | 12.50 A | 6.25 A |
| 2,000 W | 166.67 A | 16.67 A | 8.33 A |
| 3,000 W | 250.00 A | 25.00 A | 12.50 A |
| 5,000 W | 416.67 A | 41.67 A | 20.83 A |
| 10,000 W | 833.33 A | 83.33 A | 41.67 A |
Frequently Asked Questions
How to convert watts to amps?
Divide watts by volts to get amps. The formula is: Amps = Watts ÷ Volts. For example, 1,800 watts at 120 volts equals 15 amps (1,800 ÷ 120 = 15). For three-phase circuits, divide by (Volts × √3): Amps = Watts ÷ (Volts × 1.732).
How many amps is 1500 watts at 120V?
1,500 watts at 120 volts equals 12.5 amps (1,500 ÷ 120 = 12.5). This means a 1,500-watt space heater will draw 12.5 amps on a standard 120V household circuit. It will fit on a 15-amp breaker, but just barely — leaving only 2.5 amps for anything else on that circuit.
How many amps does a 1000 watt microwave draw?
A 1,000-watt microwave draws about 8.33 amps at 120V (1,000 ÷ 120 = 8.33). However, the actual draw may be higher because microwave wattage ratings refer to cooking power, not total electrical consumption. A 1,000W microwave may actually draw 1,400–1,700 watts from the outlet, or about 11.7–14.2 amps.
How many amps is 3000 watts?
It depends on the voltage. At 120V, 3,000 watts = 25 amps (3,000 ÷ 120 = 25) — too much for a single 20-amp circuit. At 240V, 3,000 watts = 12.5 amps (3,000 ÷ 240 = 12.5) — easily handled by a 15-amp 240V circuit. This is why high-wattage appliances use 240V.
Why do I need to know watts to amps conversion?
Knowing the amp draw of your devices is essential for electrical safety. Circuit breakers are rated in amps, not watts. By converting watts to amps, you can determine if a device will overload a circuit, what size breaker you need, and what wire gauge is required. Overloading a circuit is a fire hazard.
How many amps can a 20-amp circuit handle in watts?
A 20-amp circuit at 120V can handle up to 2,400 watts maximum (20 × 120 = 2,400). However, the NEC 80% rule for continuous loads limits you to 1,920 watts (2,400 × 0.80 = 1,920) for devices running more than 3 hours. At 240V, a 20-amp circuit handles up to 4,800 watts (3,840 watts continuous).
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