M-Ratio

Also known as: M, Harrington M, effective M

Your stack divided by the cost of one orbit (small blind + big blind + total antes), measuring how many rounds you can survive.

Popularized by Dan Harrington, the M-ratio measures stack health in orbits rather than big blinds. The formula:

\[ M = \dfrac{\text{stack}}{\text{SB} + \text{BB} + \text{antes}} \]

It tells you how many full rounds you can fold before blinding out, which is why it captures ante pressure better than a raw bb count. Harrington's zones: green (M ≥ 20) full play, yellow (10-20) tightening, orange (6-10) push/fold mode, red (1-5) desperate shoving, dead (< 1) any-two jam.

"Effective M" multiplies by the fraction of a full table still seated, since a short-handed table costs you blinds faster. In the modern game, stack-to-blind ratio in big blinds is the more common metric, but M remains useful precisely because it folds antes and table size into one number that maps to push/fold urgency.