Ohm's Law Calculator
Voltage, current, resistance and power from any two.
Enter your values
Enter the voltage (v) you are working with.
Enter the current (a) you are working with.
Enter the resistance (ω) you are working with.
Enter the power (w) you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Voltage
- 12 V
- Current
- 2 A
- Resistance
- 6 Ω
- Power
- 24 W
Working
- 1V = I × R = 2 × 6 = 12 V
Quick answer
Ohm's law states V = I × R, and power follows as P = V × I.
V = I·R, P = V·I
At a glance
| What it does | Voltage, current, resistance and power from any two. |
|---|---|
| Category | Science |
| Inputs needed | Voltage (V), Current (A), Resistance (Ω), Power (W) |
| Formula | V = I·R, P = V·I |
| Cost | Free — no sign-up, no download |
How to use the Ohm's Law Calculator
- 1Fill in any two of the four boxes.
- 2Leave the unknowns blank.
- 3Read all four values.
Inputs explained
- Voltage (V)
- Enter the voltage (v) you are working with.
- Current (A)
- Enter the current (a) you are working with.
- Resistance (Ω)
- Enter the resistance (ω) you are working with.
- Power (W)
- Enter the power (w) you are working with.
Frequently asked questions
What is one ohm?
The resistance that lets one amp flow when one volt is applied across it.
Does Ohm's law apply to AC?
For resistive loads yes. Reactive circuits need impedance, which accounts for phase between voltage and current.
What do I need to enter into the Ohm's Law Calculator?
Just 4 values: voltage (v), current (a), resistance (ω), power (w). Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Ohm's Law Calculator work out the answer?
Ohm's law states V = I × R, and power follows as P = V × I. It applies the formula V = I·R, P = V·I and shows the working so you can check each step by hand.
Is the Ohm's Law Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.