Watts to Amps Calculator

Convert watts to amps for DC, single-phase AC, and three-phase AC circuits. Enter power in watts and voltage to calculate current in amps. Essential for determining wire gauge and circuit breaker size.

W
V

CURRENT

15 A

MILLIAMPS

15,000 mA

CIRCUIT TYPE

DC

FORMULA

I = P / V

Watts to Amps β€” Conversion Table

Watts120V AC240V AC12V DC
100 W0.83 A0.42 A8.33 A
200 W1.67 A0.83 A16.67 A
500 W4.17 A2.08 A41.67 A
750 W6.25 A3.13 A62.5 A
1,000 W8.33 A4.17 A83.33 A
1,500 W12.5 A6.25 A125 A
1,800 W15 A7.5 A150 A
2,000 W16.67 A8.33 A166.67 A
3,000 W25 A12.5 A250 A
4,000 W33.33 A16.67 A333.33 A
5,000 W41.67 A20.83 A416.67 A
10,000 W83.33 A41.67 A833.33 A

πŸ’‘ How to Convert Watts to Amps

Converting watts to amps tells you how much current a device draws from the circuit. This is essential for choosing the right wire gauge, circuit breaker size, and ensuring your electrical system can safely handle the load.

Watts to Amps Formula

DC Circuit: I = P / V
Single-Phase AC: I = P / (V Γ— PF)
Three-Phase AC: I = P / (V Γ— PF Γ— √3)

Where:
I = Current in amps (A)
P = Power in watts (W)
V = Voltage in volts (V)
PF = Power factor (0–1, AC only)

Example: 1,500-Watt Space Heater on 120V

I = 1,500 W / 120 V = 12.5 amps

A 1,500W space heater draws 12.5A on a 120V circuit. This requires at least a 15-amp breaker, but is better on a 20-amp circuit per the NEC 80% rule (12.5A is 83% of 15A).

Why Converting Watts to Amps Matters

Appliances are often rated in watts, but your circuit breakers and wiring are rated in amps. To determine if your circuit can handle a load, you must convert the wattage to amperage and compare it to your breaker rating.

Common US Appliances β€” Watts to Amps at 120V

ApplianceWattsAmps (120V)Min. Breaker
Phone Charger5 W0.04 A15 A
LED Bulb10 W0.08 A15 A
Window Fan200 W1.67 A15 A
Refrigerator400 W3.33 A15 A
Vacuum Cleaner1,200 W10.0 A15 A
Space Heater1,500 W12.5 A20 A
Electric Oven (240V)5,000 W20.8 A30 A

Wire Gauge Guide (NEC)

The NEC specifies minimum wire gauge based on amperage:

Breaker SizeWire Gauge (AWG)Common Use
15 A14 AWGLighting, bedroom outlets
20 A12 AWGKitchen, bathroom, garage
30 A10 AWGDryer, water heater
40 A8 AWGElectric range, large AC
50 A6 AWGLarge appliances, sub-panels

References

  • NFPA 70 β€” National Electrical Code (NEC), 2023 Edition
  • Ugly's Electrical References, 2023
A 1,500-watt space heater draws 12.5 amps on a 120V circuit. At 83% of a 15-amp breaker, the NEC recommends a 20-amp circuit for continuous use.

Watts to Amps Calculator FAQ

πŸ”— Related Calculators

Amps to Watts CalculatorConvert amps to watts for DC and AC circuits. Enter current (amps) and voltage to calculate power in watts using Watt's Law. Supports single-phase and three-phase AC.Watts to Volts CalculatorConvert watts to volts for DC and AC circuits. Enter power (watts) and current (amps) to find voltage. Supports power factor for AC circuit calculations.Watts to kWh CalculatorConvert watts to kilowatt-hours (kWh) to calculate energy consumption and electricity costs. See how much power your appliances use per day, month, or year.Volts to Amps CalculatorConvert volts to amps using Ohm's Law (with resistance) or Watt's Law (with power). Calculate current draw for any DC or AC electrical circuit.