Ohms Law Calculator
Last updated: June 2026 · Free · No sign-up required
Enter values above and click Calculate to see your result instantly.
Quick reference
Ohm's law relationships:
| Know | Find voltage | Find power |
|---|---|---|
| I and R | V = I x R | P = I^2 x R |
| V and R | — | P = V^2 / R |
| V and I | — | P = V x I |
| P and I | V = P / I | — |
apps Small jobs, done in one click
Everyday calculators are the workshop drawer of the site — quick utilities for the moments when you need a number now and a phone calculator won't cut it. Age, date difference, GPA, fuel cost, time-to-decimal, password strength — pick a tool and you're one click from your answer.
speed Loads in under a second
Every tool is plain HTML + JavaScript with the calculation logic compiled in. No spinner, no "verifying browser" splash, no five-second wait while ads load. Hit the page, fill the form, get the answer. Slow tools waste your time and ours.
devices Works on every device
Responsive design tested down to a 320px-wide phone screen. The input fields use native number/date keyboards on iOS and Android, the calculate button is thumb-sized, and the result still reads big and bold on the smallest screen. No app to download, ever.
sentiment_satisfied No funny business
No newsletter pop-ups, no "create an account to see the answer", no fake countdown, no fake stock counter, no upsell. Two ad slots per page (clearly labelled as Advertisement) keep the site free — that's the whole business model.
Interpretation guide
Quantities and units:
| Symbol | Quantity | Unit |
|---|---|---|
| V | Voltage | Volts |
| I | Current | Amperes |
| R | Resistance | Ohms |
| P | Power | Watts |
Formula & methodology
Formula: V = I x R; P = V x I; combine to get P = I^2 R = V^2 / R
Ohm's law states that voltage equals current times resistance (V = IR). Combined with the power law (P = VI), the calculator solves for any of the four quantities — voltage, current, resistance, or power — from any two known values. These relationships are the foundation of circuit analysis, used to size resistors, check current draw, and verify a component stays within its power rating.