Watts (W) to Amps (A) Converter

What Is a Watts (W)?

A watt measures electrical power. It tells you how fast a device uses or produces energy. Common examples include lights, motors, heaters, and power supplies.

What Is a Amps (A)?

An amp, or ampere, measures electrical current. It tells you how much electric charge flows through a circuit. Higher current means more charge flows each second.

How to Convert Watts (W) to Amps (A) manually?

For a basic DC or resistive load, divide watts by volts. The formula works when the circuit does not require a power factor adjustment.

Formula

$A = W \div V$

Step by step Guide

1. Enter the power in watts.
2. Enter the voltage in volts.
3. Divide watts by volts.
4. Read the result in amps.

Practical Example

A 1,200 W device uses 120 V.

$A = 1,200 \div 120 = 10 A$

The device draws 10 amps under these conditions.

DC watts to amps calculation

DC circuits use a simple watts to amps formula. You only need power in watts and voltage in volts. This method suits batteries, DC motors, and many solar systems.

Formula

$A = W \div V$

Step by step Guide

1. Enter the DC power in watts.
2. Enter the DC voltage.
3. Divide watts by voltage.
4. Check the current in amps.

Practical Example

A 600 W DC load runs at 24 V.

$A = 600 \div 24 = 25 A$

The calculated DC current equals 25 amps.

AC three phase watts to amps calculation

Three phase AC systems need a different formula. The calculation depends on voltage, power factor, and the voltage type you enter.

Formula

For line to line voltage:

$A = W \div (\sqrt{3} \times V_{LL} \times PF)$

For line to neutral voltage:

$A = W \div (3 \times V_{LN} \times PF)$

Use the power factor from the equipment data when available.

Step by step Guide

1. Enter the three phase power in watts.
2. Select line to line or line to neutral voltage.
3. Enter voltage.
4. Enter the equipment power factor.
5. Apply the matching formula.
6. Check the current in amps.

Calculation with line to line voltage

Line to line voltage measures voltage between two phase conductors. Use the three phase formula when the system provides line to line voltage.

Formula

$A = W \div (\sqrt{3} \times V_{LL} \times PF)$

Step by step Guide

1. Enter power in watts.
2. Enter line to line voltage.
3. Enter power factor.
4. Multiply voltage by $\sqrt{3}$ and PF.
5. Divide watts by that result.

Practical Example

A three phase load uses 10,000 W at 480 V with a 0.90 power factor.

$A = 10,000 \div (1.732 \times 480 \times 0.90)$

$A \approx 13.37 A$

Calculation with line to neutral voltage

Line to neutral voltage measures voltage between one phase and neutral. Use the three phase formula designed for line to neutral voltage.

Formula

$A = W \div (3 \times V_{LN} \times PF)$

Step by step Guide

1. Enter three phase power in watts.
2. Enter line to neutral voltage.
3. Enter the power factor.
4. Multiply voltage by 3 and PF.
5. Divide watts by that result.

Practical Example

A three phase load uses 10,000 W at 277 V with a 0.90 power factor.

$A = 10,000 \div (3 \times 277 \times 0.90)$

$A \approx 13.39 A$

Typical power factor values

Do not use typical power factor values for accurate calculations. Use the equipment manufacturer's stated value whenever possible.

Watts (W) to Amps (A) Conversion Chart

Reference chart at 120 V using $A = W \div V$.

Note: These values use 120 V and assume a simple watts to amps calculation without power factor.

The NEC 80% Rule for Commercial Circuits

The common NEC 80% rule helps account for continuous loads. A circuit often uses only 80% of its breaker rating for continuous load. Check the applicable NEC requirements before sizing equipment.