How do you convert amps to watts?

Multiply amps by volts. Formula: Watts = Amps × Volts. Example: 15 amps at 120 volts = 1,800 watts (1.8 kW).

How do you convert watts to amps?

Divide watts by volts. Formula: Amps = Watts ÷ Volts. Example: 2,400 watts at 240 volts = 10 amps.

Amps to Watts Calculator

Convert amps and volts to watts — or watts and volts to amps. Works for DC (12V, 24V, 48V) and AC (120V, 240V) systems.

Conversion direction

Current?

Voltage?

Power output

1,800 watts (1.80 kW)

Voltage120 V

Current15.00 A

Power1,800 W

Kilowatts1.800 kW

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How to Use This Calculator

Choose conversion direction

Select whether you're converting Amps + Volts to Watts (finding power from current and voltage) or Watts + Volts to Amps (finding current draw from power and voltage). Both conversions use the same formula rearranged.

Enter your values

Input the known values. For current (amps), check the device label, circuit breaker, or fuse rating. For power (watts), check the appliance nameplate. For voltage, select your system — US household outlets are 120V, large appliances use 240V, and solar battery systems commonly use 12V, 24V, or 48V DC.

Use the quick presets

Click a preset for common scenarios: a standard 15A household circuit, a 400W solar panel, a 30A RV hookup, or a 50A RV service. These pre-fill realistic values to get you started quickly.

The Formula

Watts = Amps × Volts (P = I × V) Amps = Watts ÷ Volts (I = P ÷ V) Volts = Watts ÷ Amps (V = P ÷ I) Kilowatts = Watts ÷ 1,000

This is Ohm's Power Law, derived from Ohm's Law (V = I × R). For DC circuits and resistive AC loads, this formula applies directly. For AC circuits with motors or transformers, the actual power factor may reduce real power below the calculated apparent power — but for most household and solar calculations, this formula gives an accurate enough answer.

Note: for three-phase AC systems, multiply by √3 (1.732) for line voltage, or use phase voltage directly. This calculator handles single-phase systems.

Example

Sizing a circuit breaker for a solar inverter

You have a 5,000W (5 kW) solar inverter connected to a 240V AC output. What size circuit breaker do you need?

ModeWatts + Volts → Amps

Power5,000 W

Voltage240 V AC

Result

Current draw20.83 amps

NEC 125% rule26.04 amps minimum

Next standard breaker30A breaker

The NEC (National Electrical Code) requires continuous loads to be sized at no more than 80% of circuit capacity — meaning the circuit breaker must be at least 125% of the calculated current. A 30A double-pole breaker is the correct choice for this 5 kW inverter.

Common Conversions Reference

1A at 12V DC12 watts

10A at 12V DC120 watts

10A at 120V AC1,200 watts (1.2 kW)

15A at 120V AC1,800 watts (1.8 kW)

20A at 120V AC2,400 watts (2.4 kW)

30A at 120V AC3,600 watts (3.6 kW)

50A at 240V AC12,000 watts (12 kW)

1,000W at 240V AC4.17 amps

400W panel at 24V DC16.7 amps

FAQ

What is the difference between amps, volts, and watts? ▼

Voltage (V) is electrical pressure — the force pushing electrons through a circuit. Current (A) is the flow rate of electrons. Power (W) is the rate of energy transfer, the product of voltage and current. The water analogy: voltage is water pressure, current is flow rate (gallons per minute), and watts are the power output of the water flow. Double the pressure OR double the flow rate and you double the power.

Why does solar use 24V or 48V instead of 12V? ▼

Higher voltage systems carry the same power with less current, which means thinner (and cheaper) wire can be used. A 1,200W system at 12V requires 100A of current — that needs very thick, expensive cable. The same system at 48V requires only 25A, allowing much smaller wire. For solar systems over 1,000W, 48V is standard because it dramatically reduces wiring costs and losses. Home solar inverters typically run at 48V DC on the battery side.

How do I know what size wire to use for a given amperage? ▼

Wire sizing depends on current (amps), not watts. Once you know the amps from this calculator, use our AWG Wire Gauge Calculator to find the right wire size. As a rough guide: 14 AWG handles 15A, 12 AWG handles 20A, 10 AWG handles 30A, 8 AWG handles 40A, 6 AWG handles 55A. Always derate for bundled wires, conduit, and long runs.

Does this formula work for both AC and DC? ▼

For DC (direct current) and resistive AC loads, W = A × V is exact. For AC circuits with inductive loads (motors, transformers), you need to account for power factor. True power (watts) = Apparent power (VA) × Power factor. For motors, power factor is typically 0.8-0.95. For simple resistive loads like heaters, incandescent lights, and most solar/battery calculations, the basic formula is accurate.