how do you calculate winning percentage preflop

[shin333]

I'm talking about the percentages that televised poker shows display preflop. I always thought it was by calculating outs and I am still sure that it has alot to do with it. But everytime I try to get the same percentage as the numbers shown on television, I dont get the same numbers.

How do you calculate winning percentages against however many people before seeing the flop? Kind of like the percentages that Phil Laak is famously known to shout out whenever he's all in preflop.