Bubble Factor
Also known as: BF, ICM bubble factor
The ratio of $EV lost when you lose a chip to $EV gained when you win one in a given all-in, a direct measure of ICM pressure.
Bubble factor quantifies how much more it hurts to lose than it helps to win in a specific confrontation. It is the ratio:
\[ \text{BF} = \dfrac{\$\text{EV lost per chip if you bust}}{\$\text{EV gained per chip if you double}} \]
A bubble factor of 1.0 is a pure chip-EV spot (early MTT, deep stacks): chips won and lost are worth the same. A bubble factor of 1.5 means losing hurts 50% more than winning helps; on a satellite money bubble it can climb to 3+ between two covering stacks. The higher it is, the tighter you must continue.
Bubble factor and risk premium are two views of the same ICM pressure: bubble factor is the loss/gain ratio, risk premium converts that into the extra equity your calling hand needs. Note it is pairwise. It differs for each opponent depending on who covers whom.
Example
On the bubble, a covered medium stack faces a chip leader's shove. Solvers give a bubble factor around 1.7 for that pairing. Required equity to call rises from 50% (BF = 1) to roughly 1.7 / (1 + 1.7) ≈ 63%, so any hand flipping at 50-55% is now a clear fold against the cover.