Ohm's Law Calculator
Voltage, current, resistance and power from Ohm's law.
Enter your values
Enter the current in A.
Enter the resistance in ohms.
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
- 20 V
- Power
- 40 W
- Current
- 2 A
- Resistance
- 10 Ω
Quick answer
V = I x R, and P = V x I.
V = IR, P = VI
At a glance
| What it does | Voltage, current, resistance and power from Ohm's law. |
|---|---|
| Category | Engineering |
| Inputs needed | Current, Resistance |
| Main output | Voltage |
| Formula | V = IR, P = VI |
| Cost | Free — no sign-up, no download |
How to use the Ohm's Law Calculator
- 1Enter the current flowing through the circuit.
- 2Enter the resistance of the load.
- 3Read the resulting voltage and power dissipated.
Inputs explained
- Current(A)
- Enter the current in A.
- Resistance(ohms)
- Enter the resistance in ohms.
Worked example
Using the values the calculator loads with:
Inputs
- Current2 A
- Resistance10 ohms
Results
- Voltage20 V
- Power40 W
- Current2 A
- Resistance10 Ω
Frequently asked questions
What if I know voltage and resistance instead?
Rearrange as I = V/R; this tool takes current and resistance as inputs since they set voltage and power directly.
What is Ohm's law used for?
It underlies almost all basic circuit design and troubleshooting for resistive loads.
What do I need to enter into the Ohm's Law Calculator?
Just 2 values: current, resistance. 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?
V = I x R, and P = V x I. It applies the formula V = IR, P = VI 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.