Energy & Workshop Math

Watts to Amps Calculator

Convert real power in watts to load current for DC, AC single-phase or balanced three-phase circuits.

Units

Your measurements

Results update as you type.

Example shown — use your own measurements.

Electrical input power — not a motor's shaft horsepower rating.

Three-phase: the line-to-line RMS voltage.

Required for AC: greater than 0 and at most 1, from the equipment nameplate.

Fractions and number formats

Use decimals (12.5), fractions (12 1/2 or 12-1/2), or explicit lengths (12ft 6in, 12′ 6″, 25 mm). A comma followed by one or two digits is a decimal comma: 12,5 = 12.5. Grouped commas mean thousands: 1,200 = 1200. Use a decimal point for ambiguous values. Scientific notation is not accepted.

Enter your measurements

Results update as you type.

About this calculator

Enter the electrical real power in watts and the circuit voltage. For AC circuits the power factor is required — check the equipment nameplate. Three-phase mode assumes a balanced load and line-to-line RMS voltage. The inverse conversion is on the amps-to-watts calculator.

How to measure

  • Use real input power and the voltage at the load. Select DC, single phase or balanced three phase.
  • For three phase, enter line-to-line voltage.
  • AC calculations require the actual power factor; this tool does not size wires or protection.

How to use this calculator

  1. Choose the circuit type: DC, AC single phase or balanced AC three phase.
  2. Enter the equipment's real electrical power in watts.
  3. Enter the circuit voltage — line-to-line for three phase.
  4. For AC, enter the nameplate power factor.
  5. Calculate for the load current in amps.

Formula

DC: current = power ÷ voltage

AC single phase: current = power ÷ (voltage × power factor)

AC three phase (balanced): current = power ÷ (√3 × line-to-line voltage × power factor)

Assumptions

  • Power is real (electrical input) power in watts; a motor's shaft rating is not input power.
  • AC uses the stated RMS voltage and power-factor model.
  • Three-phase loads are assumed balanced; voltage is line-to-line.

Common mistakes

  • Omitting AC power factor when using real watts.
  • Using line-to-neutral voltage in a line-to-line three-phase model.
  • Treating current arithmetic as breaker or conductor approval.

Worked example

Try it: press “Load example” above the form.

1,000 W at 230 V single phase with PF 0.8 draws 1000 ÷ (230 × 0.8) ≈ 5.4 A.

Limitations

No conductor or breaker sizing, code compliance, or unbalanced/harmonic analysis.

Frequently asked questions

Why does AC need power factor?

Real AC power equals voltage × current × power factor for single phase. Balanced three phase also uses √3 with line-to-line voltage. Omitting power factor can understate current.

Does current determine a breaker size?

No. This is power arithmetic. Continuous loads, motor starting, conductor ampacity, protection and local requirements must be checked separately.

What does the worked example show?

1,000 W at 230 V single phase with PF 0.8 draws 1000 ÷ (230 × 0.8) ≈ 5.4 A.

Which assumptions should I check before using the result?

No conductor or breaker sizing, code compliance, or unbalanced/harmonic analysis.

Reviewed by Codex AI editorial agent (Editorial, 2026-11-12) · Codex independent specialist-review AI agent (educational arithmetic/source review; not licensed human approval) (Electrical, 2026-11-12).

Sources

Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.

Calculation documentation · Updated 2026-11-11 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.

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