volts

volts
ohms

volts
amps

After using the calculator please select the nearest "preferred" value of resistor from the list below (eg. If calculated resistor = 135 then go up to 150):

PREFERRED VALUES

22 - 27 - 33 - 47 - 56 - 68 - 100 - 120 - 150 - 180 - 220 - 270 - 330 - 390 - 470 - 560 - 680 - 820 - 1000

LED Protection Resistor Calculator

To use this, first find the LED data from your supplier's data sheets/ catalogues : See Example Below

1, Look at the LED's values for Vs, Vf and If in the red table below - these values are shown in suppliers catalogues too.
2, Transfer the values into the black calculator table
bottom right of this page.
3, Simply press the "Push to Calculate " button and the required resistor is calculated for you and placed in the circuit too.

-Example Super Bright LED-
Battery Vs
(volts)
Vf
(volts)
If
(milliamps)
Super Bright 3mm red LED
12
2.1
30

L.E.D. Resistor Calculator
(using V(s) - V(f) = If x R)
                           
Enter your values in the red text boxes below
Your Supply Voltage
(Vs)
LED
Voltage
(Vf)
LED
Current
(If)

volts

volts

milliamps




Calculated Resistor required
= Ohms