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Ohm's Law Calculator

Variable Legend

V= voltage (volts)I= current (amperes)R= resistance (ohms Ω)P= power (watts)

Ohm's law

The fundamental relationship.

Solve for any variable

Current
Resistance

Power formulas

Three equivalent forms of the power equation.

From V and I
From I and R
From V and R
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Pro Tip

Most household circuits are 15A (US) or 20A. A 15A/120V circuit can handle up to 1,800W. Running appliances above this trips the circuit breaker.

Difficulty:Beginner

Did you know?

Georg Ohm published his law in 1827. It was initially rejected by scientists — the Royal Society awarded him the Copley Medal 14 years later once it was proven experimentally valid.

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Reviewed May 2026
Used 44K+ times
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