Quote Originally Posted by littleogre
I have mainly been useing unseen/outs-1. That seems to be the easiest for me. Ie a gs on the flop would be 47/4-1 or 10.75
Trainer has this right. The Rule of 2 and 4 uses an "estimate" of 50 unseen cards. With it, your Gutshot has a 4/50 or 8% chance of hitting on the turn.

The actual odds are 4/47 or 8.51%. When you use the Rule of 2 and 4, you very slightly underestimate your chances of hitting your outs, and you keep everything in rounded whole numbers.

One you know it's 8%, you use (100 / 8) - 1 = 11.5 to 1 to get your odds of hitting.

It may seem a technical point, but tons of VERY good players use the Rule of 2 and 4 because it's quick, easy, and accurate in the right way for strategic planning - just slightly underestimating.