55 · Calculators

Ohm’s Law Calculator

Fill in any two of voltage, current, resistance and power to get the other two.

Fill in any two values to find the other two.

Result

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How to use the ohm’s law calculator

  1. Enter any two values.
  2. Leave the other two empty.
  3. Read the results.

The formulas

  • V = I × R (Ohm’s law)
  • P = V × I
  • P = I² × R = V² ÷ R

Here V is volts, I is amps, R is ohms and P is watts.

Examples

12 V across 6 Ω

2 A · 24 W

1,000 W heater on 230 V

4.347826 A · 52.9 Ω

Questions

Does it work for AC?

For resistive loads like heaters and bulbs, yes. Motors and electronics have reactance, which Ohm’s law alone doesn’t cover.

Is this safe for mains work?

It’s a calculator, not safety advice. Mains electricity can kill; use a qualified electrician.