tinytinker.tools✦electronics✦ohm's law calculator

ohm's law calculator

solve for any variable in V = IR. includes a LED resistor calculator.

solve for

V — voltage (V)

I — current (A)

R — resistance (Ω)

power (W)

240 mW

V = I × R
P = V × I
I = V / R

led resistor calculator

find the correct current-limiting resistor for an LED.
formula: R = (V_supply − V_LED) / I_LED

supply voltage (V)

led forward voltage (V)

red≈2.1V green≈2.2V blue≈3.2V white≈3.3V

led current (mA)

typical: 10–20 mA

resistor value

145 Ω

use nearest standard value

resistor power

58 mW

use ≥ 0.12W rated resistor