Electrical / 09
LED Resistor Calculator
Calculate a series resistor in Ω and the nearest E24 standard value from LED voltage and current in A.
How it works
R = (Vs − Vf) / I; resistor dissipation = (Vs − Vf) × I
A 5 V supply, 2.0 V LED, and 0.02 A target current require 150 Ω, also an E24 value. Calculated resistor dissipation is 0.06 W.
FAQ
Is current entered in mA?
No. Enter amperes: 20 mA is 0.02 A.
Is the nearest E24 value always suitable?
No. The nearest value is chosen by absolute resistance difference. A lower resistance increases current; verify actual current and component ratings.
Which resistor power rating should I choose?
Choose a rating above the calculated dissipation with margin for operating conditions and the manufacturer’s derating guidance.