simple led circuit and switch resistor help

I need a circuit with two large blue leds and a one switch it needs to be run off of a nine volt battery and I cant figure out what sized resistors I need and how many i might need?

Grathio8 years ago
It depends if your LEDs are wired in parallel or series. The calculator on this page is very simple and should help you figure it out.

A typical blue LED might have forward voltage of 3v and 25mA. If you run it off of 9v and wire them in series you need a 120 ohm resistor. But check the exact specifics on your LEDs to be sure.