[JulioYalil]

don't try to make it too complicated. if u have 5 outs just multiply that number by 4 and that's ur chance of winnin by the river (5 outs times 4 = 20%). forget about whether your opponent hits or not. the 2-4 rule is more than enough for any practical calculation in hold em.

so now that u know ur chance of winnin (1 out of every 5) it means u need 4 to 1 on ur money to make a breakeven call.

EXAMPLE:

hero: 8s7s
villain: KcKh
flop: 8c Th 2d
pot: $1000
villain bets $250 and is all in

the pot now is $1250 and u have to call $250. 1250/250 = 5 so u r gettin 5:1. u only need 4:1 to breakeven (from previous calculation) so makin a call here is profitable in the long run.

hope this helps.