Ohm's Law Calculator
Enter any two of voltage, current, resistance or power and get the other two, using Ohm's law and the power formula.
Resistance
46 Ω
- Voltage
- 230 V
- Current
- 5 A
- Power
- 1,150 W
230 V across 46 Ω drives 5 A, using 1,150 W.
How it's worked out
- Ohm's law
V = I × R230 V = 5 A × 46 Ω - Power
P = V × I1,150 W
- Mains electricity is dangerous. Leave wiring work to a qualified electrician.
The formulas
V = I × R · I = V ÷ R · R = V ÷ I · P = V × I
Examples
230 V and 5 A means 46 Ω and 1,150 W. A current of 2 A through 6 Ω needs 12 V and uses 24 W.
Mains electricity can kill. Use this for learning and planning, and leave wiring to a qualified electrician.
Questions people ask
What is Ohm's law?
The voltage across a resistor equals the current through it times its resistance: V = I × R. Rearranged, I = V ÷ R and R = V ÷ I.
How do I find the current a device draws?
Divide its power by the voltage. A 1,150 W heater on 230 V draws 5 A.
How is power related?
Power is voltage times current: P = V × I. It can also be written P = I² × R or P = V² ÷ R.
Does it work for AC?
For simple resistive loads such as heaters and kettles, yes. Motors and electronics have a power factor, so their real current can differ.
About this calculator
Formula and rules last checked 25 October 2026Written and tested by the CalculatorDex teamReport a problem