UtilityBaseDeveloper Tools
Ohm's Law Calculator
Enter any two of voltage, current, resistance, or power and get the other two instantly.
Updated July 10, 2026
How to use the ohm's law calculator
- 1Enter any two of voltage, current, resistance, or power.
- 2Leave the other two fields blank.
- 3Read the calculated values instantly.
- 4Change an input to explore the relationships.
Common uses
- Sizing a resistor for an LED or circuit
- Finding the power draw of a component
- Physics or electronics homework
- Checking voltage, current, or wattage on a build
Frequently asked questions
What is Ohm's law?
Ohm's law states that voltage equals current times resistance: V = I × R. It means the current through a conductor is proportional to the voltage across it and inversely proportional to its resistance.
How do I calculate power?
Power in watts is voltage times current: P = V × I. Using Ohm's law you can also write it as P = I²R or P = V²/R, which is why entering any two of the four values lets the calculator find power and the rest.
Which two values do I need?
Any two of voltage, current, resistance, and power. The calculator recognizes the pair you entered and applies the right formula, whether that's V and I, R and P, or any other combination.
About this tool
The Ohm's law calculator solves for voltage, current, resistance, and power from any two known values. It applies V = I × R together with the power relationships P = V × I, P = I²R, and P = V²/R, so whatever pair you enter, it fills in the remaining two. It's a quick reference for electronics, electrical work, and physics homework — for example, 12 volts across 12 ohms gives 1 amp and 12 watts. Everything is calculated in your browser.
Like most tools on UtilityBase, the ohm's law calculator runs entirely in your browser — nothing you enter is uploaded or stored on a server. It's free to use with no account required. Browse more developer tools here.
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