This is a discussion on How do you calculate pre-flop starting hand percentages? within the online poker forums, in the Learning Poker section; For example, when I see pocket 2s vs AK, it's 51% vs 49%.
When it's Pocket Kings vs A 3, then it's 65% vs 35%
Start with any random 2 cards. Based on the showdown value of those 2 cards AGAINST THE REMAINING PLAYERS, the odds can be derived. So your 23 offsuit will lose to every other hand in a PF showdown. There is an absolute linear correlation when only considering those 2 PF cards. So your 2 cards will fall on that linear chart somewhere. And based on probabilities of improving your original 2 cards, recalculated odds can alter your standing on that 2 card linear chart. So 87 suited is higher on that chart than 87 offsuit.
Extrapolate for the flop, turn, river, but not for the showdown because at that point there are no more odds of winning, there is only the truth.
I'm not familiar with any calculator enough to state whether or not they take into consideration how big the original table is. 10,9,8 6 seats etc. But any calculator would work if it knows how many hands are left to act.