What is a cooler in poker?

A spot where a very strong hand runs into a stronger one and the money goes in, because folding would have been a mistake: K♠K♥ against A♦A♣ before the flop, a set under a bigger set, a flush under a bigger flush.

How often does set over set happen?

Rarely: once two players already hold different pocket pairs, both flop at least a set on 1.04% of the flops, about one in 96. Counting the hands where they do not both hold pairs, it is far rarer.

Should I fold kings before the flop in case of aces?

No. Holding K♠K♥, a single opponent holds aces 0.49% of the time; against everything else, kings are ahead. Losing to aces is a cooler, not a mistake.

Cooler in Poker: When a Strong Hand Loses Without a Mistake

By the Poker Puzzle Trainer team · Published October 21, 2026

A cooler is a spot where a very strong hand runs into a stronger one and the money goes in, because folding would have been the mistake. K♠K♥ against A♦A♣ before the flop has 18.7% equity; a set of sevens under a set of queens keeps 4.3%. Coolers are rare and they cost money, but they are results, not errors: the decision to play the hand was right.

Compute an equity

The classic coolers, computed

Cooler	When	Equity of the losing hand
K♠K♥ vs A♦A♣	before the flop	18.7%
7♦7♣ vs Q♠Q♥ on Q♦ 7♥ 2♣, set under set	on the flop	4.3%
K♥9♥ vs A♥4♥ on Q♥ T♥ 2♥, flush under flush	on the flop	4.4%

Each line is an exact count over every remaining board. On the flop, the smaller set and the smaller flush are drawing almost dead: each wins only if one card comes, the last seven (7♠, four of a kind) or the J♥ (a straight flush).

How rare they are

Set over set. When two players hold different pocket pairs, both flop at least a set on 1.04% of the flops: 180 of the 17,296 flops left with 7♦7♣ against Q♠Q♥, about one flop in 96.
Kings into aces. Holding K♠K♥, one given opponent holds aces 0.49% of the time: 6 combinations among 1,225.

Rare, but over thousands of hands they will come. That is why a cooler is part of variance, not a sign that you played badly.

Cooler or mistake?

A cooler is a hand you would play the same way again. Folding K♠K♥ before the flop to avoid aces, or a set on a dry flop to avoid a bigger set, would give up far more expected value than the rare cooler costs. A bad beat is different: the losing hand was far ahead and an unlikely card turned it around; for the bigger set or flush above, the 7♠ or the J♥ would be a bad beat. The real mistake is calling off with a weak hand and blaming a cooler. Judge the decision, not the result, and keep coolers from turning into tilt.

Keep going

Why a set is so hard to fold: set vs trips.
The best possible hand on a board: the nuts in poker.
What equity means: poker equity.

Today's spot →

Sources

Equities enumerated exactly over every remaining board; flop and combination counts done by enumeration.