LED current limiting resistor calculation

To calculate resistor value needed for a simple led circuit use ohms law


R=Vcc−VfIf




Where

• Vcc is the supply voltage
• Vf is the voltage drop across the LED
• If is the current through the LED measured in Amperes (Amps/A)
• R is the resistance, measured in Ohms (Ω).

For example i have the following LED

Vf------------> 3V

IF------------>10MA

and power supply Vcc -------> 5V

substituting values in equation gives:

                 R    =        5V-3V  

                                10mA

               

                       = 200ohm and you can select nearest standard value 220ohm