Short-Stack Poker: the Math of 10bb to 20bb

Most poker strategy is written for deep stacks, where the interesting decisions happen on the turn and river. Tournaments are not deep-stack poker. The average stack shrinks as blinds climb, and a huge share of your all-important pots are played somewhere between 10 and 20 big blinds. This is the zone that actually decides who cashes and who busts, and it runs on different math than the 100bb game. This guide covers how that math works, why postflop play nearly vanishes, where small raise trees survive, and when the whole thing collapses to all-in-or-fold.

Why short-stack math is its own game

At 100bb you have room to open, get three-bet, call, and still play three streets with meaningful decisions. At 15bb you do not. If you open to 2bb and get shoved on, you are not folding much and you are not flatting to play a postflop pot, you are calling off or folding. The stack simply is not deep enough to maneuver.

The technical way to say this is that the stack-to-pot ratio after a raise is tiny. Once you put a raise in and get action, the pot is already a large fraction of what you have left, so any further betting commits you. When commitment is automatic, the real decision is whether to enter the pot at all and with what plan. That decision is preflop. This is why short-stack tournament poker is, above almost everything else, a preflop game, and why owning a correct preflop baseline for these depths is worth so much.

The transition zone: 15bb to 20bb

It is tempting to lump everything under 20bb into a single push/fold chart, but that flattens a real distinction. At 15bb to 20bb the solve still uses small raises. In the Simple GTO tournament ranges the 8-max open at 20bb is around 2bb, the same modest sizing you would expect deeper, because a small raise does the job when stacks are short and the ante is already sweetening the pot. That open is not always a commitment. You can open with a plan to fold to a shove with the weaker part of your range and to call off with the stronger part.

So at these depths you are carrying two tools at once. Some hands prefer a min-raise, keeping a fold or a call in reserve depending on what comes back. Other hands prefer to skip the raise entirely and move all-in, taking the pot down now or racing when called. Which hand takes which line is not obvious, and it shifts by position and by the exact stack. That is precisely the kind of detail a solved range settles and intuition usually gets wrong.

The 20bb open-shove versus min-raise question

The single most common short-stack question is whether to open-shove or min-raise at around 20bb. The honest answer is that the solve does both, and the split is deliberate.

A min-raise risks less and keeps your strong hands in a range that can continue profitably. It also lets you fold the bottom of your opening range when someone jams over the top, which an open-shove never can. The cost is that a min-raise gives active opponents a chance to reshove and put you to a decision. An open-shove flips that trade. It applies maximum immediate pressure and denies opponents the cheap reshove, at the cost of risking your whole stack every time and folding out hands you might have wanted to keep in.

Because both lines have real merit, the correct strategy mixes them by hand strength, blockers, and position. Reshove-friendly hands and hands that hate getting jammed on lean toward the direct all-in; hands that play well raise-first lean toward the 2bb open. Trying to memorize this from feel is a losing battle, which is one more reason to work from a solved reference at each depth rather than a one-size chart.

The collapse to all-in-or-fold near 10bb

Push down toward 10bb and the min-raise tree finally gives way. At 10bb there is not enough behind a raise to fold or maneuver, so the strategy compresses toward open-shove-or-fold from most seats. This is the classic short-stack regime, and it is where Nash-style push/fold thinking earns its reputation: with almost no postflop left, the game genuinely reduces to a jam-or-muck decision and the ranges become wide and mechanical.

The important insight is that this collapse is gradual, not a cliff. Somewhere between 20bb and 10bb, hand by hand and seat by seat, raise trees drop out and shoving takes over. A player who only owns a 10bb shove chart is guessing everywhere above it, and a player who plays every short stack like it is 20bb is min-raising into spots that demand a shove. You want the whole gradient solved, which is exactly what the Simple GTO tournament ranges provide from 100bb all the way down to 10bb.

How the ante bends everything

None of this happens in a vacuum. Modern tournaments use the 12.5% ante, and the Simple GTO tournament solves are built on it. The ante puts dead money in the pot before a single voluntary chip goes in, and that changes the price on every aggressive action. When you steal, you risk your raise to win the blinds plus the ante, a better ratio than a no-ante pot. When you shove, you are jamming into a pot that already rewards you for pushing people off marginal holdings.

The practical result is that correct short-stack ranges are wider than a rake-free, ante-free intuition suggests. The ante is the reason a 20bb steal can profitably include hands that would be too loose without it, and the reason short-stack shoves reach deeper into the deck than beginners expect. Solving on the real ante structure is what keeps these ranges honest instead of theoretical.

Reshoving is the other half of the zone

Opening is only half of short-stack play. The other half is what you do when someone else opens and you are the short stack behind. At 10bb to 20bb the answer is usually a reshove, a re-raise all-in over their open, rather than a flat call. Flatting an open with 15bb leaves you a tiny stack in a bloated pot with position problems, so the solve overwhelmingly prefers to jam or fold when it wants to continue.

The reshove is a high-leverage weapon because it attacks the opener's whole range. They opened wide, expecting to give up sometimes, and your all-in makes them commit a big chunk of their stack to continue. That fold equity is why correct reshoving ranges are wider than beginners expect: you win a lot of pots outright, and when called you still have equity from the ante-boosted pot. The exact reshove range depends on your stack, their stack, and their opening position, which is another reason a solved reference beats a gut read. Study the depths where reshoving lives and you stop leaving chips on the table every time you fold a hand that was a profitable jam.

Sizing stays small, and that is on purpose

New short-stack players often assume that shorter means bigger opens, as if you need to raise more to protect a small stack. The solve says the opposite. Opens stay small, around 2bb, even down at these depths. A small open accomplishes the goal of getting money in and applying pressure while risking as little as possible, and the ante already inflates the reward. Oversizing your opens at 15bb to 20bb just donates equity every time you have to give up. If you want the full logic of why solved sizings are so restrained, preflop raise sizing walks through it across depths.

What to actually take to the tables

Short-stack play has a reputation for being simple, and in one sense it is: fewer streets, fewer decisions, less room to get fancy. But simple is not the same as easy, and the 10bb to 20bb zone hides more nuance than the push/fold cliché admits. The min-raise tree lives longer than most players think, the open-shove-versus-raise split is deliberate rather than random, and the ante widens everything.

The players who master this zone are not the ones with the fanciest postflop game. They are the ones who have drilled the correct preflop decisions cold, so that when they are sitting on 17bb in the cutoff with a marginal hand, they already know whether it is a raise, a shove, or a fold. That is a memorization and repetition problem, and it starts with having the right answers in front of you. And because these decisions repeat constantly as the blinds climb, small edges here compound faster than anywhere else in a tournament. A player who is right at 15bb one percent more often than the field is quietly winning races and stealing pots all day long, and that gap is the difference between a steady casher and someone who keeps busting just short of the money. Study the transition depth by depth, learn where raises give way to shoves, and the most decisive stretch of any tournament stops being a guessing game.