Ohms Law Calculator

Calculate voltage, current, resistance, or power using Ohms Law and the power equation.

Result

Fill in the fields above, then press Calculate.

An Ohm's Law calculator finds voltage, current, resistance, or power from any two known electrical values using V = IR and P = VI.

Select which value you want to solve for, then enter at least two of the remaining known values. The calculator uses Ohm's Law and the power equations to find all four values.

Examples

Find voltage: 2A through 50 ohms

V = I x R = 2 x 50 = 100 V. Power: P = V x I = 100 x 2 = 200 W.

Find resistance: 120V, 60W bulb

R = V^2 / P = 120^2 / 60 = 240 ohms. Current: I = P / V = 60 / 120 = 0.5 A.

Frequently Asked Questions

What is Ohm's Law?
Ohm's Law states that the voltage across a conductor is directly proportional to the current flowing through it, with resistance as the proportionality constant: V = I x R.
Can I use this for AC circuits?
This calculator handles DC circuits and purely resistive AC circuits. For AC circuits with capacitance or inductance, impedance (Z) replaces resistance and calculations become more complex.
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Quick Tips

  • •Remember the Ohm's Law wheel: V = IR, I = V/R, R = V/I, P = VI, P = I²R, P = V²/R.
  • •Double-check your units — voltage in volts, current in amps, resistance in ohms, power in watts.