What is Geometric Bet Sizing & How Do You Use It?

Geometric bet sizing — sounds pretty math-y and complicated, doesn’t it?

It’s actually not that complicated at all. In fact, there’s a good chance you’ve basically applied this concept at the table before, even if you didn’t know it by name.

When used in the proper situations, geometric bet sizing will help you win your opponent’s whole stack more often when you’re holding a strong hand. That’s a pretty appealing feature if you ask me.

This article covers the concept of pot geometry as well as geometric bet sizing.

Let’s dive in!

What is Pot Geometry?

Pot geometry refers to how the bet size used on each street impacts the final pot size of a hand. Put simply, big bet sizes result in bigger pots and small bet sizes result in smaller pots.

To exemplify this, let’s compare two scenarios in which the only difference is the bet sizes used by the aggressor on each street.

Example 1: Betting Small on the Flop

Suppose you raise preflop to 2.5 big blinds (bb) from the cutoff with A♠ K♦ and the small blind calls.

With 6bb in the pot, the flop comes Q♠ J♣ T♥. The small blind checks and you decide to bet small for 2bb (a 33% pot-sized bet). The small blind calls.

With 10bb in the pot, the turn is the 7♣. The small blind checks, you bet 7.5bb (75% pot), and the small blind calls.

With 25bb in the pot, the river is the 4♠. The small blind checks, you bet 18.75bb (75% pot), and the small blind calls.

Result: You drag a 62.5bb pot with the nut straight.

Example 2: Betting Big on the Flop

Let’s run through that exact same example. The only difference will be the use of a larger bet size on the flop.

Again, you raise preflop to 2.5 big blinds (bb) from the cutoff with A♠ K♦ and the small blind calls.

With 6bb in the pot, the flop comes Q♠ J♣ T♥ and the small blind checks. This time you go for a relatively big 4.5bb bet (75% pot) and the small blind calls.

With 14.5bb in the pot, the turn is the 7♣. The small blind checks, you bet 10.9bb (75% pot), and the small blind calls.

With 36.3bb in the pot, the river is the 4♠. The small blind checks, you bet 27.2bb (75% pot), and the small blind calls.

Result: You drag a 90.7b pot with the nut straight.

What can be learned from this example?

The bet size used early in the hand had a profound impact on the final size of the pot. You got to win nearly 50% more money just by increasing that flop bet size from 33% to 75% pot. 

This goes for preflop as well. I don’t want to get derail this article by getting super deep into the math, but suppose that the preflop raise size in the examples was 2bb instead of 2.5bb. This reduces the size of the pot on the flop to 5bb. If you went with the same bet sizing scheme from example #1, the final pot would be 51.9bb instead of 62.5bb pot. That results in a huge difference in expected value (EV) for some hands in your range.

Pro tip: When playing live games, most players have static preflop ranges, meaning that they do not adjust their calling range based on the preflop raise size. Against such players, it makes mathematical sense to raise to a bigger size by default with a slightly tighter range than usual.

To learn how to absolutely crush weak players who don’t adjust enough versus larger bet/raise sizes, read How to Snowball Your Winnings vs Bad Poker Players.

What is Geometric Bet Sizing?

Geometric bet sizing refers to a single bet size (as a percentage of the pot) that can be used on each of the remaining streets so that the bettor goes all-in (for that same bet size) as the final bet. It doesn’t need to be exactly perfect, but it should be close.

Geometric sizing is often used by poker solvers in their solutions. This is because one of the primary strategic goals in poker is to win your opponent’s whole stack with your strongest hands. Geometric bet sizes accomplish that in a very effective way.

For example, suppose you’re on the turn and the pot is 14bb. You have 93bb behind. The geometric bet size in this spot is 139%. That means you would bet 19.5bb on the turn to set up an all-in bet of 73.5bb on the river.

Let’s run through one more example, but make it a 3-bet pot this time.

Suppose you 3-bet preflop with AA and bet small on a J22 flop. There is 31bb in the pot and you have 85bb behind.  The geometric bet size in this spot is 76%. You would bet 23.5bb on the turn to set up an all-in bet of 61.5bb on the river.

There is a mathematical formula for this, though it’s quite unproductive to remember (it’s easier to simply estimate the geometric bet size in-game). If you want to see it, expand the section below.

Final Thoughts

In order to effectively use geometric sizing in-game, you must study it away from the table. By looking at solver solutions for different spots, you can learn which situations lend themselves to this kind of strategy.

Keep in mind that geometric bet sizing is not appropriate for every scenario. For example, if geometric bet sizing would require overbetting, but you do not have the nut advantage, you should put this concept to the side and go for more typical sized bets.

That’s all for this article! I hope you enjoyed it and that you learned something new from it. As usual, if you have any questions or feedback please let me know in the comment section down below and I will do my best to answer!

Till’ next time, good luck, grinders!