Ohm's Law Calculator — Voltage, Current, Resistance, Power

Calculator

An Ohm's law calculator finds the remaining two of voltage, current, resistance, and power from any two known values using V = I × R and P = V × I.

Ohm's Law Calculator

Runs in this browserUses the displayed formula

Inputs are calculated only in this browser. Results assume a purely resistive load; AC circuits with reactance need impedance instead.

Examples

Known pair

Voltage

Current

Result

—

What is it

Ohm's law states that current through a conductor is proportional to voltage and inversely proportional to resistance (V = I × R). Combined with the power formula P = V × I, knowing any two of voltage (V), current (A), resistance (Ω), and power (W) is enough to calculate the rest. This calculator assumes a purely resistive DC circuit; AC circuits with reactance need impedance and power factor instead.

V = I × R · P = V × I = I² × R = V² / R

How to use

1Pick the pair of values you know (for example voltage + current).
2Enter the two values.
3Press calculate to get the other two values.

Reference

Ohm's Law Calculator — Voltage, Current, Resistance, Power Reference
Input	Resistance	Power
V = 12V, I = 2A	6Ω	24W
V = 220V, R = 100Ω		484W
P = 60W, V = 12V	2.4Ω

Sources & standards

BIPM — The International System of Units (SI Brochure) - BIPM
IEC Electropedia — International Electrotechnical Vocabulary - IEC
MDN Web Docs: Client-side web APIs - MDN Web Docs

FAQ

What is the resistance when 12V drives 2A?

R = V / I = 12 / 2 = 6Ω, and the power is P = 12 × 2 = 24W.

Can I use an Ohm's law calculator for AC circuits?

Yes for purely resistive loads, but AC circuits with reactance such as motors or capacitors need impedance and power factor, so results will differ.

Is Ohm's law calculator input sent to a server?

No. This calculator runs in your browser and does not send input to a server.