Ohms Law + Power Calculator

Voltage (V)

Current (A)

Resistance (Ω)

Reset

Please enter any two values.

⚠ Exceeding 40 mA on any digital pin can damage the ATmega chip. Use a Transistor or Buffer. For a guide, click HERE

Ohm’s Law is a fundamental principle in electronics that describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit.

V = I × R

From this, you can rearrange to calculate any of the three:

Voltage (V) = Current × Resistance
Current (I) = Voltage ÷ Resistance
Resistance (R) = Voltage ÷ Current

Using Ohm’s Law, you can also calculate power (P) — the rate at which electrical energy is consumed:

P = V × I

Other forms:

P = V² ÷ R
P = I ² × R