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The Bubble Factor and the Bubble Factor Table
The Bubble Factor and the Bubble Factor Table
Andrey Vasiliev avatar
Written by Andrey Vasiliev
Updated over a week ago

The display of bubble factors is a major feature of ICMIZER 3. Whenever you perform a Nash calculation you will see differently colored circles next to each opponent which will indicate their bubble factor against you. The bigger the bubble factor, the more pressure you are putting on this opponent meaning that they will need more equity to call your pushes (as the most obvious example of applying the bubble factor).

Here is the sample screenshot with bubble factors versus big stack on the bubble of a classic 9 max SNG tournament with 3 payouts:

As you can see, BTN has the smallest bubble factor and can actually call with the widest range (9.4%) versus our wide push.
SB, who has a larger stack, has a larger bubble factor and can only call with a 3.5% range, and BB who has the biggest stack and has a huge bubble factor of 2.7 versus us can only call with top 2.7% hands against our almost any-two push.

The Bubble Factor concept is not very intuitive and can be hard to grasp for beginner players.

So let's start slow and build it up from the simpler bricks. Let's say we are in Chip EV mode, either playing cash or tournament with 1 prize, like Spin & Go.
In this case, the absolute change in our stack worth of doubling up or busting from the tournament is the same. So if we double up from 500 chips to 1000 or bust, technically both outcomes change our stack worth by exactly 500 chips. Since both outcomes have the same absolute value (but a different sign, +500 or -500), winning 50% of the time would be enough to make us indifferent and justify the potential all-in.

So, in this case, in order to calculate the bubble factor, we would take the absolute change of our stack if we lose (500) and divide it by absolute change if we win (500) and we get 500/500 = 1. So in Chip EV mode or in tournaments with 1 prize the bubble factor is usually 1, you can play according to classic cash game pot odds.

Now in SNG or MTT tournaments where we have more than 1 payout, we have to use ICM to convert chips into their tournament prize equity value in order to compare decisions.

So let's look at our example and play on the BB with 4000 chips. Initially, his stack is worth 29.23%

If he loses to UTG who has him covered, he gets nothing. If he wins, however, he doesn't even guarantee himself an ITM (although this win is big) and his new stack will be worth 40.16%:

Now its time to meet the Bubble Factor formula:
Bubble Factor = ChangeInOurTourneyEquityIfWeLose / ChangeInOurTourneyEquityIfWeWin or (EvBegin - EvLose)/(EvWin - EvBegin).

We can now calculate the bubble factor according to this formula: (29.23 - 0)/(40.16-29.23)= 29.23 / 10.93 = 2.67

So in this tournament situation, winning 4000 chips only adds 10.93% of the tournament prize pool to BB player. But losing costs him 29.23% of the prize pool, even though the chips that he wins or loses are the same.

If you click only any bubble factor you will see the detailed bubble factor table which shows bubble factors of each player against each other player. As we see, the bubble factor for BB versus UTG is indeed 2.67, so our math was correct.

How can we use Bubble Factors?

Great question! We can take the bubble factor and quickly estimate how much equity we need to call an all-in against a specific opponent. With bubble factor 1 we can say for simplicity that we will need 50% equity versus their range.

If the bubble factor is bigger, we can use the following formula to estimate our required all-in equity:

Equity = BubbleFactor / (BubbleFactor + 1) * 100%

So with 2.67 bubble factor we can estimate Equity as 2.67 / (2.67 + 1) = 0.7275 or 73%.

We hit Calculate and see that our calling range is 99+.

With 99 being the worst calling hand, let's check the details for this calculation, namely how much equity 99 have versus CO's huge pushing range.

As we can see, it is pretty close to 72%, which we've calculated earlier. In fact, it is just slightly less because we weren't taking SB and antes into account with our bubble factor analysis.

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