Ohm's Law Calculator

Ohm's Law defines the relationship between voltage, current and resistance in an electrical circuit. This calculator lets you find any one of the four key electrical quantities - voltage (V), current (I), resistance (R) and power (P) - by entering the other two.

A
Ω
Voltage (V)
12 V
Current (I)
2 A
Resistance (R)
6 Ω
Power (P)
24 W

How it works

Select which quantity you want to find, then enter the two known values. Power is always derived as P = V x I.

Formula
V = I x R | I = V / R | R = V / I | P = V x I = I² x R = V² / R

Example. A 12V battery connected through a 6Ω resistor drives a current of 2A and dissipates 24W of power.

Frequently asked questions

What unit is resistance measured in?

Resistance is measured in Ohms (Ω). 1 Ohm is defined as 1 Volt per Ampere - the resistance that allows exactly 1A of current when 1V is applied.

What is electrical power?

Power (in Watts) is the rate at which electrical energy is transferred or used. P = V x I, so a 12V circuit drawing 2A consumes 24W - the same as a modest light bulb.

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