How to use the Ohms Law Calculator
The Ohm's law calculator finds voltage, current, resistance or power when you know any two.
Open the Ohms Law Calculator →
What you need to enter
- Voltage (V)
- Current (A)
- Resistance (Ω)
- Power (W)
The formula
V = I × R, P = V × I, so P = I²R = V² ÷ R.
Worked example
Using the default values in the calculator:
- Voltage (V): 12
- Resistance (Ω): 6
| Voltage | 12 V |
| Current | 2 A |
| Resistance | 6 Ω |
| Power | 24 W |
Tips for better results
- Fill in any two fields and leave the rest blank.
- Use base units (volts, amps, ohms, watts).
Common mistakes to avoid
- Entering milliamps as amps.
- Entering more than two values that disagree.
Please note: Results are estimates for general use. For safety-critical work such as electrical or building projects, check with a qualified professional and local codes. See our Disclaimer.