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Ohm's Law Calculator

Calculate voltage, current, resistance, and power using Ohm's Law. Enter any two known values to instantly solve for the remaining two.

Enter Two Known Values

Select which quantity to solve for, then enter the other two

Solve For
V
Voltage
Volts (V)
I
Current
Amperes (A)
R
Resistance
Ohms (Ω)
P
Power
Watts (W)
Input Values
Unit Prefixes

Circuit Diagram

Voltage
—
V

All Calculated Values

Voltage (V)—
Current (I)—
Resistance (R)—
Power (P)—

Ohm's Law Triangle

V = I × R
I = V / R
R = V / I

Power Formulas

P = V × I
P = I² × R
P = V² / R

Resistor Color Code

Black0
Red2
Yellow4
Green5
Orange3

All Ohm's Law Formula Variants

Voltage

V = IR = P/I = √(PR)

Current

I = V/R = P/V = √(P/R)

Resistance

R = V/I = V²/P = P/I²

Power

P = VI = I²R = V²/R