Led Info needed please

[bsbuk]

so i ve ordered all my leds, and i know i need a 10ohm resistor. but when i enter info in the following site http://led.linear1.org/led.wiz it says i need a 10ohm resisitor, i want to know how to work out resistors.
the details i entered for the site are
3.6
1.8
20
2
and the details for my leds are
Source Material GaInN
Emitting Colour YELLOW
Emitting Wavelength(nm) 585-595
Size 1.2 x 0.8 mm
Intensity (mcd) 60-100
Viewing Angle (deg) 120
Forward Voltage (V) 1.8-2.4
Forward Current (mA) 20-30

any info appreciated, thanks

[tibor28]

resistance= output voltage- the voltage your led needs/current your led needs in AMPS (1000mA=1A)
so it would be 3.6 (if you are using the power board and 5v if your are using the motherboard) -2.4/30= 40ohms

[GhoSt]

a ten ohm resitor is standard with most psp led mods. But i would sugest 0603 led's.