Ohm's Law Calculator
Enter any two of voltage, current and resistance and get the third, plus the power.
Results
Voltage
—
V
Current
—
A
Resistance
23
Ω
Power
2300
W
What this tool does
Ohm's law is the single relationship that ties voltage, current and resistance together, and almost every other electrical calculation starts from it. Fill in the two values you know and leave the third blank.
Formula
U = I × R , P = U × I
Variables
| Symbol | Meaning | Unit |
|---|---|---|
u | Voltage | V |
i | Current | A |
r | Resistance | Ω |
U | Voltage | V |
I | Current | A |
R | Resistance | Ω |
P | Power | W |
Worked example
- Voltage230 V
- Current10 A
- Resistance23 Ω
- Power2300 W
Limitations
- Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.
Frequently asked questions
Which two values do I need to enter?
Any two of voltage, current and resistance. Leave the third one empty and the calculator fills it in, along with the power. If you enter all three, the values you typed are used as they are and only the power is derived.