Which values can I enter in the Ohm's Law calculator?

Enter any two known quantities from voltage, current, resistance, and power. The calculator automatically solves the other two.

Does the calculator support engineering units?

Yes. It supports common SI units such as millivolts, milliamps, kiloohms, megohms, milliwatts, and kilowatts.

Can I use zero in an Ohm's Law calculation?

Zero is supported when the relationship remains finite, such as zero volts across a positive resistance. Open-circuit or otherwise indeterminate combinations are explained instead of displaying Infinity or NaN.

Ohm's Law Calculator

Enter any two electrical quantities to solve the remaining voltage, current, resistance, and power values instantly.

Ohm's Law Calculator

Enter any two electrical quantities to solve the remaining voltage, current, resistance, and power values instantly.

Live relationship view

Resistive DC circuit

VVoltage: 5 V
ICurrent: 5 mA
RResistance: 1 kΩ
PPower: 25 mW

Calculation details

Calculated using

I = V ÷ R

5 V ÷ 1,000 Ω = 0.005 A = 5 mA

P = V² ÷ R

5² ÷ 1,000 = 0.025 W = 25 mW

Formula reference

Ohm's Law relationships

Voltage · V

V = I × R

V = P ÷ I

V = √(P × R)

Current · I

I = V ÷ R

I = P ÷ V

I = √(P ÷ R)

Resistance · R

R = V ÷ I

R = V² ÷ P

R = P ÷ I²

Power · P

P = V × I

P = I² × R

P = V² ÷ R

This calculator uses non-negative magnitude relationships for simple resistive DC circuits. Real components also have tolerances, temperature limits, and power ratings.

Practical examples

Common calculations

5 V across 1 kΩ5 mA · 25 mW

12 V at 2 A6 Ω · 24 W

24 W in 6 Ω12 V · 2 A