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What is M?
In Harrington on Hold'em Volume II, Harrington reviewed the concept of M and the strategies based on your M.
M is your chip stack divided by the total of the blinds and antes. It tells you the number of rounds of the table you can survive before getting blinded off.
Unlike simply comparing your stack to what is posted in the big blind, the M takes into account both blinds and antes. As a result, you push the action more often with a wider range of opening hands, using the edge of acting first pre-flop to your advantage.
As your M drops, your need for more chips becomes more desperate and you must be more aggressive.
It is also a good idea to know your opponents M, since they also may be pushing with a wider range of hands when there M is getting low.
My additional thought on M is that you may want to adjust your M based on the time remaining in a round. For example, if the round just began your M is a good formula. However, if there are only a few minutes left in a round, you may want to adjust your M for the next level of blinds.
The Zones based on your M and the strategies
In general, the M tends to come into play towards the end of a tournament. Of course, if you've taken a big hit on your stack, you may need to use it earlier. Also, the M comes into play earlier on many online one table satellites, especially those turbo events.
Here is a brief review of the strategies using M:
Green Zone: M is 20 or more. You can play your style as you have ample chips.
Yellow Zone: M is 10-20. You need to be somewhat more aggressive with high pairs and high card hands. With small pairs and small connectors be more conservative.
Orange Zone: M is 6-10. You need to open with more hands and try a small ball approach. Again, be more careful with those small pairs and suited connectors. However, if you are considering opening with an all-in move, the small pairs and suited connectors are playable.
Red Zone: M is 1-4. Move all-in with a wide range of cards, like two face cards, small pairs or better, suited connectors. Your position at the table doesn't matter.
Keep in mind the concept of first in vigorish; this means that when no one is in the pot, the player who makes the first pre-flop raise has the initiative. Therefore, when your M is 3, if there is a 50% chance your opponents will fold, move all-in first pre-flop with almost any two cards.
When your M is below 2, move all-in with anything....any Ace, King, Queen, medium strength hand, connectors, pairs, etc.
Additional points on M
Know your opponents M since these players will be pushing the action. And your positional advantage of acting last will decrease.
Effective M is a way to adjust for short tables. To calculate your M when the table is short simply take your M and multiply it by the number of players left/10. So, if your M is 8 and there are 5 players left, your effective M is really 8 multiplied by .5 or 4. The result is that you need to be taking more chances. Also at a short table, your weak cards plus good pot odds really equals a playable situation.
This is a solid concept since it forces you to play when your stack is low relative to your survival rate. It makes your decision making easier since it is math based.
UPDATE: I need to provide more information on this concept. This may be something that I have not used and should be using as an end game strategy. I will provide more information soon (added 6/23/09)...note: In Harrington's book he writes: "playing correctly around inflection points is the most important single skill of no-limit hold 'em tournaments." And he follows with his introduction of M.