Ohm's law calculator
Four quantities, two relations, and every rearrangement worth having on one page.
V
A
ohm
Power from V x I
24W
- Resistance from V / I
- 6 ohm
- Current from V / R
- 2 A
- Voltage from I x R
- 12 V
- Power from I squared R
- 24
- Power from V squared over R
- 24
Show the working
- Voltage = 12
- Current = 2
- Resistance = 6
- Power from V x I = 12 * 2 = 24
- Resistance from V / I = 2 > 0 ? 12 / 2 : 0 = 6
- Current from V / R = 12 / 6 = 2
- Voltage from I x R = 2 * 6 = 12
- Power from I squared R = 2^2 * 6 = 24
- Power from V squared over R = 12^2 / 6 = 24
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
Scenarios & local history
Compare a saved scenario
Recent calculations
The formula
- V = I R
- P = V I = I^2 R = V^2 / R
Fill in the two you know and read the matching output; the others are computed from whatever you left at its default.