M-ratio

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In no-limit or pot limit poker, a player's M-ratio is a measure of the health of his chip stack as a function of the cost to play each round. A high "M" means the player can afford to wait a number of rounds before making a move. A player with a low "M" must act soon or be weakened by the inability to force other players to fold with aggressive raises.

Invented by and named after Paul Magriel, the formula is:

For example, eight-way in a no limit game hold'em game with blinds of $50/$100, an ante of $10, and a stack of $23,000 has an M-ratio of 100:

Poker player Dan Harrington defines several "zones" in which the M-ratio may fall:

M-ratio	Zone name	"Optimal" strategy
M ≥ 20	Green	Most desirable situation, freedom to play conservatively or aggressively as you choose
10 ≤ M < 20	Yellow	Must take on more risk, hands containing small pairs and small suited connectors are useless
5 ≤ M < 10	Orange	Main focus is to be first in whatever you decide to play, preserve chips
1 ≤ M < 5	Red	Your only move is to move "all-in"
M < 1	Dead	You are completely dependent on luck to survive