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Electrical & Lighting · Conversion · Free

Watts to Amps Calculator

Convert electric power in watts (W) to current in amps (A). Pick the circuit type — DC, AC single-phase or AC three-phase (line-to-line or line-to-neutral) — enter the power, voltage and power factor, then press Calculate. The current appears in amps and milliamps. Everything runs locally in your browser.

Watts to Amps: I(A) = P(W) / V(V) — AC adds the power factor; three-phase divides by √3·PF·V (line-to-line) or 3·PF·V (line-to-neutral).

Used only for three-phase current.

Not used for DC — the DC formula has no power factor.

STEP 1

Choose the circuit type

Direct Current (DC), AC single-phase, or AC three-phase. Three-phase adds a voltage-type choice: line-to-line or line-to-neutral. AC modes also ask for the power factor (0 to 1).

STEP 2

Enter power and voltage

Type the power in mW, W or kW and the voltage in mV, V or kV — scientific notation like 2e2 works too. The swap button flips the calculator to amps-to-watts if you need the reverse.

STEP 3

Press Calculate, read amps

The current appears in amps (A) and milliamps (mA), shown to at most ten significant digits. Copy either readout to your clipboard, or press Reset to start over.

How watts become amps

What is the DC watts-to-amps formula?
The current I in amps (A) is equal to the power P in watts (W), divided by the voltage V in volts (V): I = P / V. Worked example: P = 200 W at V = 40 V gives I = 200 / 40 = 5 A.
How does AC single-phase differ?
The phase current I in amps is equal to the power P in watts divided by the power factor PF times the RMS voltage V: I = P / (PF × V). The power factor of a resistive impedance load is 1. Worked example: P = 2000 W, V = 110 V, PF = 0.8 gives I = 2000 / (0.8 × 110) = 22.72727 A.
What about AC three-phase?
For a line-to-line voltage the phase current is I = P / (√3 × PF × V); for a line-to-neutral voltage it is I = P / (3 × PF × V). So 3000 W at PF 1 across 400 V is 4.330127 A line-to-line but exactly 2.5 A line-to-neutral — the voltage type changes the denominator.
Which power factor should I use?
Typical values: resistive load and incandescent lamp 1; fluorescent lamp 0.95; induction motor at full load 0.85 (no load 0.35); resistive oven 1; synchronous motor 0.9. Do not use typical values for accurate calculations — measure or check the nameplate.
When does the calculator show an error?
Voltage of 0 V is rejected (the current would divide by zero), and so is a power factor outside 0 to 1 for AC. A result beyond the number range reports "Result is too large to display" instead of printing Infinity; zero power is always valid and gives 0 A.

Privacy: every calculation runs in your browser tab — no value you type is sent anywhere. Copy result uses your clipboard only. Results are ideal circuit-theory figures; verify real installations with a multimeter.