MDF Calculator
Enter the pot and the bet to get the minimum defense frequency, the bluff break-even (alpha), and the equity a call needs. Instant, in your browser.
How to use it
Enter the pot. The pot size before your opponent's bet.
Enter the bet. The amount they bet into it.
Read the numbers. MDF, alpha, required call equity and the balanced bluff ratio.
MDF = pot ÷ (pot + bet) — the fraction of your range you must keep to stop a bet from auto-profiting as a bluff. The calculator also returns alpha (how often a bluff must work), the equity a call needs, and the balanced value-to-bluff ratio for the bettor.
MDF vs pot odds
They answer different questions. Pot odds / required equity tell one hand whether calling is profitable right now. MDF tells your whole range how much to defend so the opponent can't print money bluffing. Use required equity for a single hand's call; use MDF to size your overall calling and raising range. See pot odds and bluff-catching.
Bigger bets, less defense
The larger the bet relative to the pot, the lower your MDF — a big overbet forces you to fold more, which is exactly why polarized ranges bet big. Balance the picture with the pot odds trainer.
A worked example
Say the pot is 100 and your opponent bets 50 — a half-pot bet. Plug those numbers in and the arithmetic is short. MDF = pot ÷ (pot + bet) = 100 ÷ (100 + 50) = 100 ÷ 150 = 66.7%. So you should continue with at least two-thirds of the range you carried to this spot. Fold more than a third and a pure bluff — a hand with no equity that only wins when you fold — turns an automatic profit.
The mirror image is alpha, the frequency a bluff must succeed to break even: alpha = bet ÷ (pot + bet) = 50 ÷ 150 = 33.3%. That is exactly the fold share (100% − 66.7%) you are allowed to give up. And a single bluff-catcher deciding whether to call needs equity = bet ÷ (pot + 2 × bet) = 50 ÷ (100 + 100) = 50 ÷ 200 = 25% to make the call profitable on its own. Notice these three numbers describe different things: MDF and alpha are properties of your whole range, while required equity is the test for one hand. A hand can clear the 25% call threshold even while your range as a whole is over- or under-defending.
- MDF — the minimum fraction of your range to continue with: pot ÷ (pot + bet).
- Alpha — how often a bluff must work to break even: bet ÷ (pot + bet).
- Required call equity — the equity one hand needs to call: bet ÷ (pot + 2 × bet).
When to ignore MDF
MDF is an equilibrium anchor — it assumes your opponent is capable of bluffing with the right frequency and is trying to make you indifferent. Real opponents rarely do this, and that is where the money is. MDF tells you the defensive baseline; deviating from it on purpose is exploitation.
Against a nit or a passive station who only bets when they have it, defending the full 66.7% is a trap — you are calling to keep a bluffer honest who never bluffs. Fold your weakest bluff-catchers and continue only with hands that actually beat their value range. Against a habitual bluffer who fires too often, do the opposite: over-defend, call down light, and let their bluffs pay you off. In both cases you are abandoning MDF deliberately because you have a read, not because the formula changed. Use MDF when you have no read, when the pool is tough, or when you are worried about being run over — and step away from it the moment a reliable tendency gives you a better line. For more on picking off bets, see bluff-catching.
MDF, overbets and polarization
Because MDF falls as the bet grows, big sizings are a tool for shrinking the range you have to defend. Face a pot-sized bet and MDF is 50%; face a 2× pot overbet and it drops to 33% (200 ÷ 600). A player betting a polarized range — nutted value hands paired with total air, and little in between — wants exactly that: the large size forces you to fold so much that the bluffs get through often enough to pay for themselves, while the value hands collect the times you are priced in to call.
This is why sizing and range shape travel together. If a bettor uses a big size, they should hold enough value to justify the bluffs; the balanced bluff share of a betting range is bet ÷ (pot + 2 × bet), the same expression as required call equity. If they overbet with a merged, medium-strength range instead, they are giving you a cheap defensive out — you can fold the bottom and never feel bad about it. As the defender, read the size: a small bet asks you to defend wide with marginal hands, while an overbet asks for fewer but stronger continues. Cross-check any single call against its price with the pot odds trainer, and see what are pot odds for the underlying math.
Frequently asked questions
What is minimum defense frequency (MDF)?
MDF is the share of your range you must continue with against a bet so that your opponent can't profit by bluffing any two cards. It equals pot ÷ (pot + bet). Defend less than this and pure bluffs become automatically profitable; defend at least this much and they break even.
How do you calculate MDF?
MDF = pot ÷ (pot + bet). Facing a half-pot bet (bet = 0.5 × pot), MDF = 1 ÷ 1.5 = 66.7%. Facing a pot-sized bet, MDF = 50%. The bigger the bet, the less you have to defend.
What is alpha (bluff-to-value) in poker?
Alpha is how often a bluff must succeed to break even: alpha = bet ÷ (pot + bet). It's the flip side of MDF. It also sets the bettor's optimal bluff ratio — for a value bet, the balanced number of bluffs is bet ÷ (pot + 2 × bet) of the betting range.
When should I not use MDF?
MDF assumes your opponent could be bluffing with anything and is a defensive baseline. Against players who rarely bluff, defend far less and just call your value-beaters; against habitual bluffers, over-defend. MDF is the equilibrium anchor, not a rule for every opponent.