Planning Three Streets Ahead: The Pot-Geometry Frame... | ThinkGTO

Most postflop mistakes do not happen on the river. They happen on the flop, three streets earlier, when you chose a bet size that boxed you into a river decision you cannot win. The single-most-common postflop leak among intermediate players is not poor river execution. It is arriving on the river with an SPR you cannot use.

This is the pot-geometry framework: decide the river goal first, then back-solve the bet sizes that get you there. Three streets of postflop are not three independent decisions. They are one decision tree, and the flop bet you pick shapes the entire tree.

The Tree, Not the Street

When you check a solver output for a flop spot in Solver+, you do not see a single number labelled "the correct bet." You see a sizing distribution with multiple sizes that each lead to different turn and river trees. The sizes are not arbitrary. Each one is engineered to land at a specific river configuration: stack-off, modest pot, give-up.

The mistake players make is to look at the flop sizing distribution, pick whichever size matches their hand strength intuition, and then play the next two streets reactively. The solver is doing the opposite. It is choosing the flop size based on where it wants to be on the river, with that specific class of hand.

Three River Goals, Three Sizing Signatures

Postflop hand classes split into three categories by river goal. Each category has a sizing fingerprint that shows up on the flop, well before the river card is even dealt:

River goal	Flop sizing signature	Hand classes
Commit (stack-off)	Larger geometric sizing chosen to reach all-in by river	Sets, two pair, strong overpairs, dominant draws
Induce / pot-control ⭐	Smaller, often non-geometric size that keeps SPR manageable for showdown	Medium-strength pairs, marginal top pair, weak overpairs deep
Give up / bluff with backdoors	Check or small probe that preserves the option to fold cheaply on bad turns	Air with backdoors, range-protection bluffs, weak made hands as bluff catchers

Most players have heard of pot control. Few have heard of its inverse: pot-commit planning. Both are the same skill viewed from different ends of the strategy.

Geometric Sizing: The Math Behind Commit Lines

If your goal is to stack-off by the river with a specific hand, the question is straightforward: what bet size, applied across N betting rounds, gets both players all-in cleanly?

For an SPR (stack-to-pot ratio) of S and N remaining streets, the geometric sizing that lands at all-in is:

bet size as % of pot = ((1 + 2×SPR)^(1/N) − 1) / 2

The math is not the headline. The headline is what the math reveals: geometric commit lines only work cleanly within a moderate SPR range. Outside that range you simply cannot get all-in across three normal-sized bets.

At a 100bb single-raised pot (SPR roughly 17), three-street geometric sizing would require bets over 100% of pot every street. Impractical and easily exploited. This is the structural reason solvers favour pot-control and small-bet strategies in deep cash SRPs: the math literally cannot deliver a clean commit line.

At a 3-bet pot 100bb effective (SPR roughly 4.5), the same formula returns a flat 58% pot per street across all three streets. That is the sweet spot, and it is why 3-bet pots produce the cleanest stack-off lines in modern GTO play.

At a 4-bet pot (SPR roughly 1.5), the math wants a 50% pot bet across just two streets, or a near-stack-off shove on the flop. This is why 4-bet pots resolve fast: the geometry has nowhere left to fit a three-street plan.

The free Geometric Sizing Calculator runs this math for any SPR and street count.

The Back-Solve in Practice

Pick a concrete spot: BB defends with a strong-but-not-nutted hand against a BTN 3-bet, going to the flop in a 3-bet pot at 100bb. SPR is roughly 4.5.

You hold a hand class that wants to stack off: a strong overpair, or top-set on a draw-heavy board. The back-solve runs like this:

River goal: Both players all-in by the river, ideally with a build-up that prices in villain's worse value hands.
Required sizing: Geometric math returns roughly 58% pot per street. Three bets of that size in this configuration get you all-in cleanly.
Flop choice: A bet near that 58% sizing, not a 33% probe and not a polarising overbet. The 33% bet leaves you with an awkward turn and a too-thin river; the overbet caps your own range visible to villain.
Turn plan: Same sizing, regardless of card (with rare exceptions for blanks that need a smaller sizing for range balance).
River plan: The remaining commit, often as a shove given the geometric setup.

The flop sizing is now a derived value, not a guess. The 9-5-3 deep dives walk through this same back-solve on two specific board textures: the BvB 3-Bet Pot Deep Dive: Mastering the 9♥ 5♦ 3♣ Rainbow Board at 100bb shows the 3-bet-pot version where geometric sizing lands cleanly, and the BvB Single Raised Pot Deep Dive: 9♥ 5♦ 3♣ Rainbow at 100bb Cash shows the SRP version where the framework forces the opposite: small bets and pot-control, because the math cannot reach all-in.

The Common Leak: SPR You Cannot Use

The leak this framework catches is subtle. You bet 33% pot on the flop with a strong hand because 33% "feels right." Villain calls. The turn pot is now roughly 1.66 times the flop pot, but your remaining stack is still huge relative to it. To get all-in on the river you would need to overbet the turn and shove the river, which is a polarising line your hand class is not actually built for. So you bet 50% on the turn, villain calls again, and now the river decision is between a thin-value half-pot bet and a river shove that prices villain into calling with their entire continuing range.

This is not a river leak. It is a flop sizing leak that compounds. The 33% flop bet committed you to a non-commit tree, but you wanted a commit tree. The solver chose differently on the flop precisely because it was already planning the river.

What to Drill

The single highest-leverage skill this framework asks for is the ability to look at a flop and immediately compute: "What is the SPR here, and which of the three goals fits my hand class?" Everything downstream follows from those two answers.

Postflop+ drills exactly this. Each spot starts with the preflop action and stack depths visible, so you can train the habit of computing the SPR and the river goal before you even pick your action. The GTO answer reveals the sizing tree, and over enough reps you start to see the back-solve before the solver shows you. Solver+ is the source of truth for the full tree visualisation if you want to study the back-solve for specific board textures.

Takeaway

Postflop is not three separate streets. It is one decision tree, and the flop bet you pick is the root that shapes every branch below it. Decide the river goal first. Compute the SPR. Pick the sizing that gets you to the goal. Drill the habit until it becomes the way you look at every flop. The river leak that costs you the most was always a flop leak with better disguise.