Ohm's law states that the voltage across a conductor equals the current through it multiplied by its resistance: V = I × R. Rearranged, I = V / R and R = V / I.

How do I calculate electrical power?

Power is voltage times current: P = V × I. Using Ohm's law you can also write P = I² × R or P = V² / R, so any two known quantities give you power.

How many values do I need to enter?

Exactly two. From any two of voltage, current, resistance, or power, the calculator solves uniquely for the other two.

Does the calculator handle units like mA and kΩ?

Yes. Each field has a unit selector (mV/V/kV, µA/mA/A, Ω/kΩ/MΩ, mW/W/kW). Values are converted to SI units internally and results are shown with a sensible prefix.

Can I compute resistance from power and current?

Yes. With power and current known, R = P / I² and V = P / I. The calculator supports every pair of inputs, including those that require a square root such as R and P.

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⚡Reference

Ohm's Law Calculator

Enter any two of V, I, R, P — get the other two instantly.

V

Voltagevolts

I

Currentamperes

R

Resistanceohms

P

Powerwatts

Formula wheel

Every relationship between V, I, R and P. Pick the row that matches your two known values.