How it is calculated
- V = I × R
- P = V × I
Fill in exactly two of voltage, current and resistance. The third value is found from V = I × R, then the power is found from P = V × I. All values must be positive.
Worked example
Voltage 12 V and resistance 6 Ω:
- Current I = 12 ÷ 6 = 2 A
- Power P = 12 × 2 = 24 W
If you enter I = 2 A and R = 6 Ω, the voltage is V = 2 × 6 = 12 V. If you enter V = 12 V and I = 2 A, the resistance is R = 12 ÷ 2 = 6 Ω.
Why your number may differ
This calculator assumes a simple circuit with fixed resistance. Real readings can differ because of meter error, and figures are rounded to four decimal places. If you fill in all three values, or fewer than two, an error is shown.