Tools

Ohm's Law Calculator

Enter any two of V, I, R, P and the other two are solved from V = I × R and P = V × I , with the identity used shown for each. Values take engineering prefixes — 4.7k , 20m , 500u — and a resistance is drawn as colour bands with its nearest E24 part.

Known values2 of 4 given

V — Voltage (volts)

I — Current (amperes)

R — Resistance (ohms)

P — Power (watts)

Try

V — Voltage

12 V

given

I — Current

2 A

given

R — Resistance

6 Ω

R = V / I

P — Power

24 W

P = V × I

Ohm’s law wheelthe ones used are highlighted

Solve for V

V = I × RV = P / IV = √(P × R)

Solve for I

I = V / RI = P / VI = √(P / R)

Solve for R

R = V / IR = V² / PR = P / I²

Solve for P

P = V × IP = V² / RP = I² × R

Resistornearest E24 part: 6.2 Ω (3.3% off)

1st digit

blue

2nd digit

black

Multiplier

gold

× 0.1

Tolerance

gold

± 5%

Accepted prefixes: G, k, m (milli), u / μ. A bare number is taken as base units.

Bands assume a 4-band ±5% part; 5-band precision resistors carry a third significant digit.