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Amps to Watts Calculator

Convert current (A) to power (W)

Select Current Type

Current (I)

Voltage (V)

Result

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Formulas

DC P = I × V

AC 1-Phase P = I × V × PF

AC 3-Phase P = √3 × I × V × PF

Quick Reference

Amps	@ 120V	@ 240V
5A	600W	1200W
10A	1200W	2400W
15A	1800W	3600W
20A	2400W	4800W
30A	3600W	7200W

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How to Convert Amps to Watts

Converting amps to watts is essential for understanding how much power an electrical device consumes. This calculation helps you determine if your circuits can handle the load and estimate energy costs.

The Basic Formula

For DC circuits and pure resistive AC loads, the formula is simple: Power (Watts) = Current (Amps) × Voltage (Volts), or P = I × V. This is derived from Watt's Law and is fundamental to electrical calculations.

AC Circuit Considerations

For AC circuits with reactive components (motors, transformers, etc.), you must include the power factor: P = I × V × PF. The power factor accounts for the phase difference between voltage and current in AC circuits.

Practical Example

A standard US household circuit is 15 amps at 120 volts. Using our formula: 15A × 120V = 1,800 watts. This means a 15-amp breaker can handle up to 1,800 watts, though for continuous loads, you should only use 80% of this (1,440 watts).

Circuit Breaker Ratings

Breaker	Max Watts (120V)
15A	1,800W (1,440W safe)
20A	2,400W (1,920W safe)
30A	3,600W (2,880W safe)

Frequently Asked Questions

To convert amps to watts, multiply the current in amps by the voltage in volts. For DC circuits: Watts = Amps × Volts. For AC circuits with reactive loads, also multiply by the power factor: Watts = Amps × Volts × Power Factor.

At 120 volts, 15 amps equals 1,800 watts (15A × 120V = 1,800W). This is the maximum capacity of a standard 15-amp household circuit. For safety with continuous loads, limit usage to 1,440 watts (80% of capacity).

No, you cannot directly convert amps to watts without knowing the voltage. Watts = Amps × Volts, so voltage is essential for the calculation. If you know the resistance, you can use P = I²R as an alternative.