Minimal Defense Frequency - 3bet 4bet 5bet
Posted by Gino Song
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Gino Song
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Minimal Defense Frequency - 3bet 4bet 5bet
I want to know how minimal defense frequency ranges are calculate for those that use it. I assume you just take the odds and just pick the best hands? Like if you get 3bet and getting 2:1 odds, you just try to defend 1/3 of what you raised with. Do we do the same for 4bets and 5bets? I'd like to know the math behind it and hand selection. Thanks.
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You already figured it out correctly. If you want to use MDF for this decision, you should get a chart as MDF is not equal to potodds. Its easy to find via google.
Lets play a quick toy game.
We open only JJ-AA and villain is only allowed to raise us pot. In this case MDF will be 50%.
So if we face 3bet we would need to defend only KK/AA and we decide to 4bet whole continuing-range and face a 5bet pot. We now only need to defend AA (50% of our range).
But imo the use of MDF in reallity is fairly questionable!
The easiest way to to calculate alpha. Alpha is (1-MDF) and represents how much fold equity is needed for a 0-equity bluff to be profitable.
Example:
BTN opens 2.5bb, SB folds, BB 3bets to 11bb, BTN 4bets to 24bb. What is BB's MDF?
Alpha = risk/(risk+reward)
BTN is risking = 24bb - 2.5bb = 21.5
BTN's reward = (0.5bb + 2.5bb + 11bb) = 14bb
Alpha = 21.5 / (21.5 + 14) = 60%
BB's MDF = 40%
Or more intuitively:
If BTN is bluff-4betting, they are risking 21.5 to win 14, therefore, they need to get that bluff through at least 60% of the time to be profitable. Therefore, BB should defend at least 40%.
(60.56% * 14bb) - (39.44% * 21.5bb) = 0
Ok so for 25nl:
EP Opens Pot 0.85
MP 3bets Pot to 2.9
EP is risking 2.9 to win 0.85 + 0.10 + 0.25 = 1.20
Alpha = 2.9 / (2.9+1.20) = 70%
So EP MDF = 30%
This is correct?
The quick way to think of it is to start where it is 50/50.
MDF = Fold Equity Needed (to begin printing $$$$)
We achieve this with a pot sized bet (your example is a bit bigger than pot it appears). So, the raiser in that spot needs you to fold 70% or more for him to print.
If you risk 2x pot, your Fold equity Needed is 67%. If you risk half pot, you need them to fold 33%, etc etc etc. Typically you will fall within those parameters. The Fold Equity # is much more important to know on earlier streets vs utilizing our opponents MDF.
MP is risking 2.9 to win 1.2, but yes that's the correct calculation.
One could argue that EP shares the MDF with everyone after MP, after all MP has to get a pure bluff through CO-BTN-SB-BB-EP. Though EP absorbs most of the responsibility of defense as the PFA.
MDF model only works if bluffs have 0 equity in the pot. That is clearly not the case in most preflop situations (some of your defends are calls so "bluffs" realize some equity), so the MDF model doesn't work. Don't use it for preflop!
ok ill use it ty
True, but you can modify it for bluffs with equity. Alpha/MDF is just a primative EV calculation.
Here's what a normal alpha calculation looks like where bluffs have no equity. To find alpha, set EV to zero and solve for fold% needed to break even.
EV = (fold% * reward) - (call% * risk)
Here's a more complicated version that assumes bluffs have equity:
EV = (fold% * pot) + call%(win% * (pot+risk) - lose% * risk)
Plug in bluff equity and solve for the fold% needed to break even. Then MDF is just 1- above.
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