I have some LED's
http://www.frozencpu.com/products/1879/ele...l?tl=g44c77s117

Power Dissipation:120 mW
Peak Foward Current: 100 mA
Continuous Foward Current:30 mA
Reverse Voltage:5 V
Forward Voltage: 3.50 V

Now my calculator says I need a standard 300ohm 1/4Watt resistor

I have some 470ohm 1/4watt resistors.
Would those be OK to use or do I need to go to radio shack?

what does the max specs say for the LED's...?

I bought mine at Jabtech as they listed the info there...so you may be alright...

they have a general voltage listing and then a max listing...so as long as you're not over the max...

I cant remember what I bought but they work great...little light for the blue leds but to heavy for the pinks I put in the wifes case...

I would probably mock one up to a 12v line and measure the voltage after the resistor...thats just because calculating the math is something I like to do...

http://www.jab-tech.com/3mm-Blue-LED-10-Pa...ng-pr-3135.html

I calculate 283.3Ohms (to run it off of 12V)

470Ohm should be fine. It'll just limit the current to 18mA so it might not burn as bright as using a 300Ohm resistor

That will work at a slightly reduced brightness. Doubtful if it will be noticeable though. But I would use a 1/2W resistor if I was going to buy some. A good rule of thumb is not exceeding 60% of the wattage value of the resistor. But if you already have the 470 1/4W resistors they will work.