Solve for voltage, current, resistance or power. Enter any two known values and the calculator computes the remaining two instantly.
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Select what you want to solve for, enter the two known values, and click Calculate.
Formulas:
V = I × R (Ohm's Law)
P = V × I (Power)
P = I² × R
P = V² / R
Ohm's Law states V = I × R. It describes the relationship between voltage, current and resistance. Power is related by P = V × I = I² × R = V² / R.
Rearrange to I = V / R. A 240V circuit with 12 ohms resistance draws 20A of current.
Power in watts: P = V × I. A 10A load at 230V draws 2,300W (2.3 kW). You can also use P = I² × R if you know resistance.
Ohm's Law applies to individual phase calculations. For total three-phase power use the Three-Phase Power Calculator, which accounts for the √3 factor.
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