Electrical

Watts to Amps Calculator

Convert real electrical power in watts to estimated current in amps across DC, single-phase, and balanced three-phase circuits.

Enter watts, voltage and power factor. Select DC or single phase for P = V × I × PF, or balanced three phase for P = √3 × V × I × PF.

Calculation and worked example reviewed 2026-11-12. See our calculation methodology.

FREE access0 signup

Electrical

Enter your measurements

US UNITS

Real power

Voltage

Power factor

0–1

Circuit

Optional: Material Price ($ / unit)

YOUR ESTIMATE

10 A2.4 kVA apparent power

Phase multiplier 1 · power factor 1.

Use line-to-line volts for balanced three phase.

Formula and example

How this calculation works

This estimator converts your entered jobsite inputs (real power, voltage, power factor, circuit) into consistent US trade units, computes the exact geometric baseline first, and then applies any selected waste or order allowance so you can verify both numbers before purchasing materials.

How does the watts to amps calculator formula work?

Current (A) = real watts ÷ (voltage × power factor × phase multiplier); multiplier = 1 for DC/single phase or √3 for balanced three phase using line-to-line voltage.

(Watts to Amps Calculator)

where:

Real power – Entered in W (default reference: $2400 W$ );
Voltage – Entered in V (default reference: $240 V$ );
Power factor – Entered in 0–1 (default reference: $1 0-1$ );
Circuit – Entered in selected option (default reference: $single$ );

The formula

Inputs to result

Current (A) = real watts ÷ (voltage × power factor × phase multiplier); multiplier = 1 for DC/single phase or √3 for balanced three phase using line-to-line voltage.

Worked example

Check the math

A 2,400 W, 240 V single-phase load at power factor 1 draws 10 A. At power factor 0.8, estimated current is 12.5 A.

Quick lookup chart

Watts to Amps Quick Reference Across Common US Voltages (PF = 1.0)

Steady-state current at unity power factor (1.0). Reactive motor loads at 0.8 PF draw 25% more current for the same real wattage.

Real Power (Watts)	120V Single Phase	240V Single Phase	480V Three Phase
1,200 W	10.00 A	5.00 A	1.44 A
2,400 W	20.00 A	10.00 A	2.89 A
4,800 W	40.00 A	20.00 A	5.77 A
9,600 W	80.00 A	40.00 A	11.55 A

Limits and field checks

Before you use this result

Power factor is not efficiency. Equipment nameplate, continuous-load treatment, starting current, harmonics and code sizing can require a different current value.

Resistive heating loads (water heaters, baseboard heat, toasters) operate near a 1.0 power factor; induction motors and compressors typically run between 0.75 and 0.90.
For continuous loads running 3 hours or more, NEC branch-circuit sizing typically requires 125% of continuous current—check equipment nameplate FLA/MCA ratings.
Use line-to-line voltage (such as 208 V or 480 V) when selecting balanced three-phase calculation mode.

Questions answered

Calculator FAQ

How many amps are 2,400 watts at 240 volts?+

At power factor 1 on a single-phase circuit, 2,400 ÷ 240 = 10 A.

Which voltage is used for three phase?+

Use line-to-line voltage with the balanced three-phase square-root-of-three formula.