I’m just starting to study hand ranges. When we say “Player A has more of a specific card rank in a spot,” for example BTN opens, SB 3-bets, BTN calls, flop comes A X X, we expect SB to have more A’s in his range compared to BTN’s wide opening range, and BTN didn’t 4-bet so AK and AA are most likely out of his range.

But we’re not talking about the absolute # of aces in each player’s range are we? We are actually talking about which player has the higher proportion of aces relative to their range.

Let’s say BTN opens ATC and calls 3-bets with ATC, and SB follows a typical hand range chart. BTN has, in absolute terms, the most # of aces in his range – every single hand with an ace. But those aces are diluted by his ridiculously wide range of ATC. So proportionally, BTN has a lesser percentage of hands with aces than SB, who has less aces absolutely (because he is not 3-betting every hand with an A in it) but whose range is much narrower than ATC so the fewer aces is SB’s range represents a higher proportion of aces. Therefore we say “SB has more aces in his range than BTN.”

Aces are a particularly significant card pre-flop, but that can change post. Let’s say the flop comes 5-5-T instead. Yes ace high is a consideration, but the bigger consideration might be “which player has more 5’s and T’s in his range?” and “which player has more pocket pairs?”

Simply counting the # of 5-X and T-X combos and pocket pair combos in each player’s range is insufficient; we would need to make those counts and then divide that # by the total hand combos in that player’s range and see who has the higher proportion of 5’s, T’s, and PP’s. Obviously not possible in game, so how do we quickly estimate this and conclude who has more 5’s, T’s, and PP’s?

And are there any common pitfalls like in my exaggerated ATC BTN range example? Situations where absolute combos and relative proportions of combos really skew the conclusions you might make?

Well we should still generally try just to the best of our abilities. When you mess around with propokertools or whatever equity calculators when you're reviewing your sessions, you'll get better at estimating this sort of thing in-game next time.

Anyway its not too important to get precise since (on the flop at least), you should still generally just be cbetting as the preflop aggressor and checking when not. Its rare when the non-aggressor's range is stronger, and very rare that that range is so much stronger that the aggressor's cbet would be a mistake.