How do I calculate amps from watts?

For a DC or unity-power-factor load, divide watts by volts. For AC motors or reactive loads, include power factor and efficiency.

Can I use this for three-phase circuits?

Yes, for a balanced estimate using line-to-line voltage, power factor and efficiency.

Is current enough to size a wire or breaker?

No. It is a starting estimate, not a substitute for electrical code, equipment instructions or a qualified design.

Current Calculator

Calculate electric current in amps from power and voltage, voltage and resistance, or power and resistance for DC and AC estimates.

Find

Supply type

Inputs

Power

Voltage, V

Example loads

Result13.6364 A

~ 13,636.36 mA

Generic breaker screening

20 A

Standard rating with a margin over calculated current. Confirm rating, trip curve, and disconnect conditions with the actual circuit design.

Copper conductor ampacity screening

1.5 mm²

Generic copper conductor ampacity screening. Installation method, bundling, aluminum conductors, long runs, voltage drop, temperature, and local electrical code need a separate design check.

Same power across supply types

Supply	Voltage, V	Current, A	Ratio to 220 V
DC 12 V	12	250	×18.33
DC 24 V	24	125	×9.17
DC 48 V	48	62.5	×4.58
AC 1-phase, 220 V	220	13.636	×1
AC 3-phase, 380 V	380	4.558	×0.33

Higher distribution voltages reduce current for the same power, which can reduce conductor size and I2R losses when the equipment is designed for it.

Amps from watts, volts and ohms

The English result set for current calculators overlaps strongly with Ohm's law and watts-volts-amps tools. The useful workflow is to solve current from the pair of electrical values the user already knows.

I = \frac{P}{V}

I is current, P power and V voltage for DC or unity-power-factor loads.

I = \frac{V}{R}

R is resistance in ohms.

I = \frac{P}{R}

Use when power and resistance are known.

I_{3 ϕ} = \frac{P}{3 V _{LL} P F η}

VLL is line-to-line voltage, PF power factor and eta efficiency.

Safety and code boundaries

Not a wire-sizing approval

Current is only one input for real electrical design. Conductor ampacity, voltage drop, breaker type, enclosure temperature, duty cycle and local code still need qualified review.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

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