The Ohm's Law Calculator is a free tool that helps you calculate ohm's law using the formula V = I x R; P = V x I (leave the unknown as 0). Enter your values above and press Calculate to get voltage, current, resistance instantly, with a full step-by-step breakdown.
What is the Ohm's Law Calculator?
The ohm's law calculator is a free online tool that helps you calculate ohm's law quickly and accurately. It applies the standard formula V = I x R; P = V x I (leave the unknown as 0) to the values you enter and, when you press Calculate, displays the result together with a clear, step-by-step explanation of how the answer was reached.
Also known as: ohm's law formula, ohms law calculator.
How to use the Ohm's Law Calculator
- Enter any two of voltage, current and resistance.
- Leave the unknown as 0.
- See all values and power.
Formula used
The ohm's law calculator is based on this formula:
V = I x R; P = V x I (leave the unknown as 0)Each term in the formula corresponds to one of the inputs explained below. The calculator performs the arithmetic for you and shows every step so you can check the working by hand if you wish.
Worked example
Suppose you enter I=2A, R=5ohm. The calculator works as follows:
| Inputs | I=2A, R=5ohm |
|---|---|
| Working | V=2x5 |
| Result | V=10V, P=20W |
Step-by-step calculation
- Apply the formula:
V = I x R; P = V x I (leave the unknown as 0) - Substitute your values: V=2x5
- Read the result: V=10V, P=20W
Inputs explained
- Voltage (V) (V) — the voltage (v) used in the calculation.
- Current (I) (A) — the current (i) used in the calculation.
- Resistance (R) (ohm) — the resistance (r) used in the calculation.
Understanding your result
- Voltage — the calculated voltage in V.
- Current — the calculated current in A.
- Resistance — the calculated resistance in ohm.
- Power — the calculated power in W.
Benefits and practical uses
The ohm's law calculator saves time and removes the risk of manual errors when you need to calculate ohm's law. It is useful for students, professionals and anyone who wants a fast, dependable answer. Results update the moment you press Calculate, work on any device, and can be copied or shared in a single click — and because the maths runs in your browser, your figures stay completely private.
Tips for an accurate result
- Keep all related inputs in the same units.
- Use the worked example above to confirm you are entering values in the right places.
- Review the assumptions below so the result fits your situation.
- Press Reset to clear everything and try a different scenario.
Common mistakes to avoid
- Entering values in the wrong unit (mismatched units give wrong answers).
- Leaving a required field empty — the calculator will ask you to fill it in.
- Rounding inputs too early, which can slightly change the result.
Assumptions and limitations
- Ideal resistive (DC) circuit.
Frequently asked questions
What is Ohm's law?
Voltage equals current times resistance (V = IR).
How do I use the Ohm's Law Calculator?
Enter your values in the fields, then press the Calculate button to see the result. Use Reset to clear the form and start again. Nothing is calculated until you click Calculate.
What formula does the Ohm's Law Calculator use?
It uses the standard formula: V = I x R; P = V x I (leave the unknown as 0). The full step-by-step working is shown with every result so you can verify it.
What information do I need to use the ohm's law calculator?
You need: voltage (v), current (i), resistance (r). Sensible example values are pre-filled so you can see how it works.
Is the Ohm's Law Calculator free to use?
Yes. Every DigiToolkit calculator is completely free, with no sign-up, no login and no usage limits.
Does the Ohm's Law Calculator work on mobile phones?
Yes. The calculator is mobile-first and works on phones, tablets and computers in any modern browser.
Do I need to install an app?
No. The ohm's law calculator runs directly in your web browser — there is nothing to download or install.
Is my data private when I use this calculator?
Yes. All calculations run inside your browser. The numbers you enter are never uploaded to a server or shared with anyone.
How accurate is the Ohm's Law Calculator?
It uses the generally accepted formula for ohm's law and computes to several decimal places. Results are accurate for the assumptions listed on this page.
Can I copy or share my result?
Yes. After calculating, use the Copy button to copy the result, or Share to copy the page link.
Why is nothing showing until I press Calculate?
By design, the calculator only computes when you press Calculate, so you can finish entering all your values first. Press Reset any time to clear everything.
What units does the Ohm's Law Calculator use?
It works with A, V, ohm. Keep your inputs in consistent units for an accurate result.