Use this led calculator except plug in the right variables in the slots. You HAVE to know the specs of the leds or you are just guessing and may burn them all out.
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Thanks for LED calculator,Can i use one resistor with bigger watt for 3*18 White LED ?
Yes you can, but the problem with that is that if one, two or a few leds burnout then the resistor is not right anymore and all the rest may burn out at once.
As Re says check the specifications CAREfully, but , you'll probably end up with 30 parallel strings of 3 LEDS and a resistor in each string