Harrington's M - Definition Of M And Basic / Effective M Scores
‘M’ in it’s simplest form is simply the ratio of the blinds (and antes if applicable) to your current chip stack. At a full table you add the 2 blinds together and divide your chips by this number to give you an ‘M’ number. For example if you have 3000 chips and the total blinds are equal to 600 then your ‘M’ is 5.

What this number tells you is how many more ‘rounds’ of the table you can survive without being blinded away. In the above example, assuming you played no hands, you can last for 5 rounds.

The basic ‘M’ score assumes a full table of 9 or 10 players. When there are less players the blinds will come around faster – and so your M is adjusted to compensate. Dividing your current M by the ratio of players at the table is know as ‘Effective M’. For example, you have 5000 chips with 5 players left – the blinds total 500, your M now equals 5000/500 = 10, however only 50% of a full table are playing so you divide by 2 for an effective M of 5.

Knowing your M score helps you by making tournament strategy adjustments based on this score. This is where Dan Harrington’s Poker Zone Theory comes into play. Your ‘M’ level (and the M of your opponents) determines which ‘zone’ you are in and so what your current strategy should be. There are 5 zones in total from the highest to the lowest these are.

Level, Zone, & Correct Play

1. Green Zone
When your M is above 20 you have many poker tournament strategy options available. Here you can raise, re-raise and still have chips left if you lose a hand.

2. Yellow Zone
Here your M is between 10 and 20. Loosen up now to stop the blinds eating away at your stack. Small pairs and suited connectors are less desirable now as your implied odds (chance of winning a big pot from a small investments) are lower.

3. Orange Zone
Your M is now between 6 and 10. Here you have lost the ability to ‘resteal’ and your stack is dwindling, you must now play aggressively to stay alive in the tournament.

4. Red Zone
M is 5 or less. Here you have lost all flexibility if you play a hand it should be all-in, try to be first into a pot to maximize the chance opponents will fold.