Welcome to my LED Current Limiting Resistor Calculator which will calculate the resistance value you need to protect one or more LEDS from a known input voltage while allowing a specified LED operating current.
The chart below shows the resistor colour coding scheme.You can use this chart to pick suitable resistors values.
The calculated resistor value will give you the required current but resistors have a tolerance associated with them. This tools suggests the values you should actually use to ensure your resistance is above the calculated value. Suggestions are given for 2,5,10 and 20% tolerance resistors. If in doubt use the 20% value. This way you will not exceed the specified LED current of 20mA.
Make sure the resistor has a rated power that is greater than the "Resistor Power" calculated above.
For more information about LEDS take a look at this page :http://www.kpsec.freeuk.com/components/led.htm