- Maths reviewed by Josh Miller
- Tested by Diana Westfield
An MDF calculator tells you how often you have to keep going against a bet so that a bluff with any two cards doesn’t print money. Facing a $75 bet into a $100 pot, minimum defence frequency is 57.1%: call or raise with at least that share of your range. The free CasinoCalcs calculator above also gives the other side of the same maths. The bettor’s bluff needs folds 42.9% of the time to break even, and a caller needs 30% equity.
MDF calculator: the four numbers
MDF = pot ÷ (pot + bet) Alpha (folds a bluff needs) = bet ÷ (pot + bet) Caller's equity needed = bet ÷ (pot + 2 × bet) Bluffs in a balanced river range = bet ÷ (pot + 2 × bet)
| Bet size | MDF | Alpha | Caller needs | Value : bluff |
|---|---|---|---|---|
| 33% pot | 75% | 25% | 20% | 4 : 1 |
| 50% pot | 67% | 33% | 25% | 3 : 1 |
| 75% pot | 57% | 43% | 30% | 2.3 : 1 |
| Pot | 50% | 50% | 33% | 2 : 1 |
| 2× pot | 33% | 67% | 40% | 1.5 : 1 |
When MDF matters, and when it doesn’t
MDF is a defence against an opponent who could be bluffing with anything. Against most low-stakes players that isn’t the case. If the player in front of you never bluffs the river, folding far more than MDF is correct, and calling to “defend” just loses money. Use it as a check on your own game, especially on the river where there are no more cards to come, and against strong, balanced opponents.
It also works the other way. If you think someone folds too much, any bluff that wins more often than alpha is profitable on the spot.
For a single call with a drawing hand, use the pot odds calculator. The implied odds calculator adds what you’ll win later, and the SPR calculator shows how deep the stacks are going into the flop.
Bluff break-even: how often a bluff has to work
A bluff breaks even when it works bet ÷ (pot + bet) of the time. That’s the other side of MDF: if your opponent folds more than this, any two cards make money.
| Bet size | Bluff needs to work |
|---|---|
| ⅓ pot | 25% |
| ½ pot | 33% |
| ¾ pot | 43% |
| Pot | 50% |
| 2× pot | 67% |
Small bluffs don’t need many folds, which is why they’re popular. They also give the other player a cheap call, so they work best when the hands they’d call with are few.
Counting how many value hands and bluffs a range holds? The poker combinations calculator counts combos after blockers.
Play for fun with money you won’t miss. If you’re spending more than you planned, BeGambleAware.org is free and confidential.