How many opponents needed to bet different draws?

[KjellBarry]

I'm a bit blank on value betting draws, so if you guys could clear up some things, that would be great.

Say we are on the button. Every round the first player to act on the flop bets, and everyone behind him calls one bet. Now, how many opponents have to call for me to bet the different draws on the flop?

I was thinking of the standard draws, such as 4 outs, 8 outs, 9 outs and 15 outs. (taken into consideration that all the outs are certain winners). If it's not much trouble, having the number of opponents needed for all the outs from 4-15 would have been great.