Percentages

[MikeyG80]

I understand how to calculate proper pot odds, but my question is, when you're playing with an odds calculator, in terms of hands vs. hands, such as the one they have on bluffmagazine.com, how do you do this math yourself. I mean, i understand the numbers and pretty much have a lot of set ups memorized, but i want to understand how to actually calculate these percentages. Example, if you are playing heads up and you have pocket 8's vs. unsuited Ace King, you are roughly 55% pre flop favorite. My question is how do you figure out the 55%? How do you figure out this scenario with a 6 person table, a 9 person table, etc. What is the formula used to do this math myself, and try to calculate this myself, instead of memorizing the odds on these calculators. i want to know how to do this longhand. Can anyone help me out???