Ohm's law calculator
Enter any two values. The other two fill in as you type.
V
A
Ω
W
Enter any two values
–
Voltage–
Current–
Resistance–
Power–
The formulas
V = I × R P = V × I
Voltage (V) is current (I) times resistance (R). Power (P) is voltage times current. From those two you can rearrange to find any value, for example I = V ÷ R or I = P ÷ V.
Worked example
A 3 kW immersion heater on 230 V draws 3000 ÷ 230 = 13.04 A, and its element resistance is 230 ÷ 13.04 = 17.6 Ω.
These formulas hold for resistive loads. For motors and other inductive loads, use the power and current calculator, which includes power factor.