Hi I'm not sure what "Luminous Intensity" means but mcd means milli-candles and ucd means micro-candles. This is not so easy to figure. You need to know how efficient the LED's are, relative to standard bulbs. It seems like I saw something that said that LEDs were not quite as efficient as fluorescent lamps but still better than incandescents. If we figured them at twice as efficient, you'd need 20W's of LEDs. Watts is just the current times the voltage. You figure this for each LED and add them all together. LEDs do require a circuit to limit the current. When you figure your total light output, you don't count the loss in the control circuit. Of course, for the final tally, you'll need to include this as well. When driving a number of LED's, it is better to drive a large number in series because you only need one current limiting circuit. The count of LED's would depend on the voltage source you have available. You'd have the total LED voltage plus the drop needed across your current limiting cicuit. Dwight