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LED calculator Answered

Is there an easy formula or an online calculator to figure out what type of resistor I would need to hook up to an LED to keep from blowing it? I know you can also have a string of LEDs and the more you use you won't need resistors. I'm just trying to figure out for different projects with different batteries, what the most efficient circuit would be. Also what does T1 3/4 mean? I noticed that on the 5mm LEDs. How does it differ from ones without a designation?


I love that calculator.

Is there an easy formula

Sure ! It's called the "Ohm's law".


Calculating the value yourself will give you a much better understanding of electronics than using the online calculator. The maths required is quite trivial, and Ohm's law can be used in so many other situations. Cheers, Pat. Pending


10 years ago

resistors have different values if you look at one you will notice bands of colour on it, you always read towards the gold band.

you could find a chart of it on the internet here

from that you could work out how many of which type of resistors you need for the LED'S you have

Note that the second link i posted (another from the top 5 google results) will also let you enter the voltage.