Bubble Factor measures how much more losing hurts than winning helps you in MTTs. It’s a measure of survival pressure and a valuable tool for understanding ICM spots. It's defined as the ratio between how much tournament equity ($EV) you’d lose getting stacked, divided by how much $EV you’d gain stacking some player in the tournament.
BF = | $EV Loss | / | EV Gain | when stacks are fully invested. Each player has a unique bubble factor against every other player in a tournament.
In a chip EV scenario, the BF is 1 because losses are equal to wins. In an ICM scenario, losses hurt more than wins, so the BF is greater than 1.