Ohm's law calculator
Enter any two of voltage, current, resistance, and power to calculate the other values. Includes formula reference.
Enter any two values — leave unknown fields empty.
Voltage (V)
Current (A)
Resistance (Ω)
Power (W)
Result
Voltage: 12 V
Current: 3 A
Resistance: 4 Ω
Power: 36 W
How to use
1. Fill in at least two known values.
2. Leave unknown fields empty.
3. Read calculated V, I, R, and P instantly.
Example
Ohm's law calculator
Enter any two of voltage, current, resistance, and power to calculate the other values. Includes formula reference.
When to use
• When you need a quick estimate without spreadsheets.
• When you want privacy — calculations stay on your device.
Limitations
• When you need certified engineering or legal calculations.
• When site-specific conditions require a professional survey.
About this calculator
Enter any two of voltage, current, resistance, and power to calculate the other values. Includes formula reference.
Frequently asked questions
Is my data uploaded?
No. All math runs locally in your browser.
Is this tool free?
Yes. No account or subscription required.