About this calculator

Ohm's law: V = I × R. Combined with power P = V × I, any two known values let you derive the others. Leave unknowns blank.

How it works

Enter your voltage (v), current (a) and resistance (ω). The result updates as you type, using the formula shown below. Nothing you enter is stored.

Limits

Results are theoretical and ignore installation method and grouping. Mains work must meet local wiring rules (BS 7671 in the UK).

Who it's for

Electricians, students and DIYers checking loads, cables and running costs.

Formula: V = I × R, P = V × I

Frequently asked questions

What does the Ohm's Law Calculator do?

Solve for voltage, current, resistance or power given any two of V, I, R or P. Ohm's law: V = I × R. Combined with power P = V × I, any two known values let you derive the others. Leave unknowns blank.

Is the Ohm's Law Calculator free to use?

Yes. Every calculator on Calcurly.com is free, works in your browser without sign-up, and can be embedded on your own website.

How accurate is the Ohm's Law Calculator?

Results are calculated in real time using the formula V = I × R, P = V × I. Treat the output as a well-informed estimate — always cross-check with local regulations, product datasheets, or a qualified electrical professional before committing to a purchase or a job.

What inputs does the Ohm's Law Calculator need?

Enter values for: Voltage (V), Current (A), Resistance (Ω). Sensible defaults are pre-filled where possible so you can start with a single change.

Can I embed the Ohm's Law Calculator on my own website?

Yes — copy the iframe snippet at the bottom of this page, or use the Embed Generator to customise the size. The embedded version stays in sync with the live calculator on Calcurly.com.