Quote Originally Posted by Jack Sawyer
My rule (or, better said, rule I follow): 1 out = 2,5% on river.
double it on turn.
It's 2%, not 2.5%. Hence 2/4 rule, not 2.5/5 rule.

Chopper's right about the limit thing. You can't use 4% if you're going to face another bet on the turn, which happens a lot in limit.

In NL you're not going to get explicit odds to call often on the flop, but you'll often have implied odds. You still need to know how to calculate this to determine if you're good or not.