Amps to Watts Calculator

Convert amps to watts for DC, single-phase AC, and three-phase AC circuits. Enter the current in amps and voltage to calculate power in watts using Watt's Law. Default values use US standard 120V AC.

A
V

POWER

1,800 W

KILOWATTS

1.8 kW

CIRCUIT TYPE

DC

FORMULA

P = I Γ— V

Amps to Watts β€” Conversion Table

Amps120V AC240V AC12V DC
1 A120 W240 W12 W
2 A240 W480 W24 W
5 A600 W1,200 W60 W
10 A1,200 W2,400 W120 W
15 A1,800 W3,600 W180 W
20 A2,400 W4,800 W240 W
30 A3,600 W7,200 W360 W
40 A4,800 W9,600 W480 W
50 A6,000 W12,000 W600 W
60 A7,200 W14,400 W720 W
80 A9,600 W19,200 W960 W
100 A12,000 W24,000 W1,200 W

πŸ’‘ How to Convert Amps to Watts

Converting amps to watts requires knowing both the current (amps) and the voltage (volts) of the circuit. The relationship between these electrical quantities is defined by Watt's Law, one of the fundamental equations in electrical engineering.

Amps to Watts Formula

The formula depends on the type of circuit:

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

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

How Many Watts Are in an Amp?

The number of watts per amp depends entirely on voltage. In US residential circuits:

  • At 120V (standard outlet): 1 amp = 120 watts
  • At 240V (large appliance): 1 amp = 240 watts
  • At 12V DC (automotive/solar): 1 amp = 12 watts

This is why a 15-amp circuit at 120V can handle up to 1,800 watts, while the same 15 amps at 240V can handle 3,600 watts.

Example: 15 Amps at 120V (US Standard Outlet)

Power = 15 A Γ— 120 V = 1,800 watts

This is the maximum wattage for a standard 15-amp circuit in US homes. Per NEC (National Electrical Code), you should only load a circuit to 80% capacity β€” so the practical limit is 1,440 watts.

Example: Three-Phase AC (Commercial)

A 30-amp, 208V three-phase circuit with PF = 0.85:
P = 30 Γ— 208 Γ— 0.85 Γ— √3 = 9,189 watts (9.19 kW)

Common US Appliance Examples

ApplianceWattsAmps at 120V
LED Light Bulb10 W0.08 A
Laptop Charger65 W0.54 A
Coffee Maker900 W7.5 A
Microwave Oven1,100 W9.2 A
Space Heater1,500 W12.5 A
Hair Dryer1,875 W15.6 A

NEC Circuit Sizing Rule

The National Electrical Code (NEC) requires that continuous loads use no more than 80% of a circuit breaker's rated capacity. This means:

  • A 15-amp breaker (120V) supports up to 1,440 watts continuous
  • A 20-amp breaker (120V) supports up to 1,920 watts continuous
  • A 30-amp breaker (240V) supports up to 5,760 watts continuous

References

  • NFPA 70 β€” National Electrical Code (NEC), 2023 Edition
  • Ugly's Electrical References, 2023 (Jones & Bartlett Learning)
  • AC Electrical Circuit Analysis β€” James Fiore, 2022
15 amps Γ— 120 volts = 1,800 watts β€” the maximum for a standard US 15-amp outlet. Per NEC, only load to 80% (1,440W) for continuous use.

Amps to Watts Calculator FAQ

πŸ”— Related Calculators

Watts to Amps CalculatorConvert watts to amps for DC and AC circuits. Enter power (watts) and voltage to calculate current in amps. Supports single-phase and three-phase AC with power factor.Volts to Watts CalculatorConvert volts to watts using current or resistance. Learn the formulas for DC and AC circuits with power factor. Includes voltage-to-wattage conversion table.Amps to Volts CalculatorConvert amps to volts using Ohm's Law (with resistance) or Watt's Law (with power). Supports DC, single-phase AC, and three-phase AC circuits.Amps to kVA CalculatorConvert amps to kilovolt-amps (kVA) for single-phase and three-phase circuits. Calculate apparent power for generator and transformer sizing.