Ohm's Law Calculator Solve V · I · R · P Instantly

Enter any two known values — Voltage, Current, Resistance or Power — and instantly calculate all the unknowns. Free, fast & accurate for students, electricians & engineers.

V = I × R

P = V × I

I = V / R

R = V / I

P = I²R

P = V²/R

⚡ Ohm's Law Calculator

Choose what to solve for, then enter the two known values

VVoltage

ICurrent

RResistance

PPower

Known Values — Enter Any Two

Voltage V

Current A

Resistance Ω

Power W

Input Multipliers

Voltage Scale

Current Scale

Resistance Scale

Power Scale

Voltage (V)

Current (I)

Resistance (R)

Power (P)

Quick Reference

Ohm's Law Formula Wheel

All 12 Ohm's Law Formulas

● 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

Session Records

Calculation History

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⚠ Note: Ohm's Law applies to linear resistive circuits at constant temperature. For AC circuits with inductors or capacitors, use impedance (Z) instead of resistance (R). Power formula P = V×I assumes unity power factor (DC or purely resistive AC).