Minimum Defense Frequency (MDF) in Poker: Formula and Application
Last updated: May 12, 2026
Minimum Defense Frequency (MDF) is the percentage of your range you must defend — by calling or raising — to prevent an opponent's bluffs from being immediately profitable. The formula is simple: MDF = 1 − (Bet ÷ (Pot + Bet)). Against a pot-sized bet, MDF is 50% — you must defend half your range or the bluff profits automatically. Against a half-pot bet, MDF rises to 67% — the bluff is cheaper, so you must defend more to make it unprofitable.
MDF is a floor, not a target: you don't need to defend exactly 50% of your range, but defending less than 50% against a pot-bet means your opponent can profitably bluff with any two cards. In practice, MDF defines the minimum folding frequency you can have before being exploited — and understanding it helps you avoid both over-folding (giving away free money to bluffs) and under-folding (calling too wide and losing to value hands). This guide explains the MDF formula, provides an MDF reference table for common bet sizes, and shows how to apply MDF to real calling decisions.
The MDF Formula Explained
The derivation is straightforward. Your opponent bets B into a pot of P. If you fold, they win P immediately — no showdown required. A bluff is profitable whenever your fold frequency exceeds B ÷ (P + B), because that is the break-even point: they risk B to win P, and they need to succeed often enough to cover their investment. So the maximum fold frequency is B ÷ (P + B), and MDF — the minimum you must defend — is the complement:
MDF = 1 − Bet ÷ (Pot + Bet)
Max Fold % = Bet ÷ (Pot + Bet)
The intuition works in both directions. Larger bets require you to fold more — the opponent is risking more per bluff, so the bluff needs to work less often to be profitable, which means you can fold more. Smaller bets are cheaper to make, which means the opponent needs to succeed more often to recover their bet — so you must defend more to keep bluffs unprofitable.
Both MDF and Max Fold always sum to 100% — they are complements. If MDF is 67%, maximum fold is 33%. If you fold 40% in that spot, you are over-folding by 7 percentage points, and any bluff — regardless of hand strength — becomes immediately profitable for your opponent.
MDF Reference Table by Bet Size
Use this reference card for the eight most common bet sizes. Each card shows the bet size as a percentage of pot, the resulting MDF, the maximum fold frequency, and the practical implication for your range decisions.
25% pot
Cheap bluff — you must defend a very wide range or bluffs print money.
33% pot
Small c-bet size — defend 3 out of every 4 hands in your range.
50% pot
Half-pot bet — defend at least 2 in 3 hands; over-folding is a common leak.
66% pot
Standard 2/3-pot size — still need to defend a solid majority of your range.
75% pot
Near pot-sized pressure — only slightly less defense required than a pot bet.
100% pot
Pot bet — defend exactly half your range or any bluff is immediately profitable.
150% pot
Overbet — you can fold more; only continue with strong hands and value.
200% pot
Large overbet — significant pressure; only call 1 in 3 hands in your range.
Note: these percentages apply to your range as a whole — the combined total of all calls and raises in a given spot. A single over-fold in one hand does not matter; systematic over-folding across your range does.
How to Apply MDF in Real Hands
Applying MDF to a real hand follows a four-step process. You do not need to run the calculation in real time at the table — the reference table above covers most situations — but understanding the steps helps you internalize the concept and spot leaks in your game.
Step 1: Identify the bet size as a % of pot
Count the pot before the bet, then express the bet as a fraction. A $60 bet into a $90 pot is a 66% pot-size bet.
Step 2: Look up or calculate MDF
Use the reference table, or apply MDF = 1 − Bet ÷ (Pot + Bet). A 66% pot bet gives MDF = 1 − 60 ÷ 150 = 60%.
Step 3: Estimate your range size in this spot
How many total hand combinations can you realistically have here? On the river after check-calling twice, your range may be 20–30 combos.
Step 4: Ensure calls + raises ≥ MDF × range
If your range is 25 combos and MDF is 60%, you need at least 15 combos that call or raise. If you only have 10, widen your call range.
Practical Example
Villain bets 66% pot on the river. MDF = 60%. You assess your range in this specific spot and find 10 strong value hands and 5 bluff-catchers — 15 total defending combos. Your total range in this spot is 25 combos. 15 ÷ 25 = 60% — you are exactly at MDF. If you fold any of those 15 combos, you drop below MDF and bluffs become profitable. If villain is over-bluffing, you should defend above 60% by calling some thinner bluff-catchers.
MDF vs Pot Odds — The Difference
MDF and pot odds are complementary tools that operate at different levels of analysis. Confusing them is a common mistake that leads to flawed reasoning.
Pot Odds
Per-hand decision
Tells you whether a specific hand has enough equity to call profitably. Answers: "Should this hand call?"
MDF
Range-level audit
Tells you how much of your entire range must defend to prevent bluff exploitation. Answers: "Am I folding too much overall?"
The key insight is that you can be at MDF while still making some individual calls that are negative EV. In a GTO framework, you sometimes call with hands that are below pot odds — not because that call is profitable in isolation, but because it keeps your range balanced and prevents bluffs from being systematically profitable. This is the trade-off between individual hand EV and range-level defense.
In practice: use pot odds when evaluating a specific hand in your range; use MDF to audit whether your overall calling strategy in a spot is leaving you exploitable to bluffs.
Common MDF Mistakes
These four mistakes account for the majority of MDF-related errors at all stakes levels.
Over-folding (most common leak)
Folding 60–70% against half-pot bets when MDF requires only 33% maximum fold. This is the most widespread and most profitable mistake for opponents to exploit. If you fold too much, every bluff prints money regardless of opponent's cards.
Applying MDF to a single hand
MDF is a range concept, not a hand concept. Saying 'I must call because of MDF' about one specific hand is incorrect. MDF tells you how many hands to defend across your range — individual hands are evaluated by pot odds and equity.
Confusing MDF with required equity
MDF (1 − B ÷ (P+B)) and pot odds (B ÷ (P+B)) use similar inputs but answer different questions. MDF is about range frequency; pot odds are about individual hand equity. Mixing them up produces nonsensical strategy.
Defending weak hands to hit MDF
MDF is a floor — always defend the hands with the best equity first, not randomly. If you need to defend 60% of your range, fill that 60% with your strongest holdings. Calling weak hands to reach a frequency quota while folding stronger ones is the wrong approach.
Definitions
Frequently Asked Questions
What is minimum defense frequency in poker?
Minimum Defense Frequency (MDF) is the percentage of your range you must defend — by calling or raising — to prevent an opponent's bluffs from being immediately profitable. When you fold more than the maximum fold frequency, your opponent profits by bluffing with any two cards regardless of their hand strength. The formula is MDF = 1 − Bet ÷ (Pot + Bet). For example, facing a pot-sized bet, MDF = 1 − 1 ÷ (1+1) = 50%. If you fold more than 50% of your range, pure bluffs become profitable. MDF is a core concept in GTO poker because it sets the floor for how often you must continue in any given spot — knowing it helps you identify and fix over-folding leaks that opponents can ruthlessly exploit.
How do you calculate MDF?
The MDF formula is: MDF = 1 − Bet ÷ (Pot + Bet). Step one: express the bet as a number (e.g., $50). Step two: add the bet to the current pot (e.g., $100 + $50 = $150). Step three: divide the bet by that total ($50 ÷ $150 = 0.333). Step four: subtract from 1 (1 − 0.333 = 0.667, or 67%). Example 1 — half-pot bet: Bet = $50, Pot = $100. MDF = 1 − 50 ÷ 150 = 67%. Example 2 — pot-sized bet: Bet = $100, Pot = $100. MDF = 1 − 100 ÷ 200 = 50%. You can also derive the maximum fold frequency directly: Max Fold = Bet ÷ (Pot + Bet). Both formulas always sum to 100%.
What is the MDF for a half-pot bet?
The MDF for a half-pot bet is 67%. Here is the full calculation: if the pot is $100 and the bet is $50 (half the pot), then MDF = 1 − 50 ÷ (100 + 50) = 1 − 50 ÷ 150 = 1 − 0.333 = 0.667, or 67%. This means you must defend at least 67% of your range — through calls and raises combined — or any bluff becomes immediately profitable for your opponent. The intuition is that smaller bets are cheaper to make, so your opponent risks less per bluff attempt. To make those cheap bluffs unprofitable, you need to continue more often. Conversely, larger bets force you to fold more because your opponent is risking more — they need your folds to be more frequent to break even on bluffs.
What is the difference between MDF and pot odds?
MDF and pot odds answer different questions. Pot odds tell you whether a specific hand has enough equity to call a bet profitably — it is a per-hand calculation. If you are getting 3:1 on a call, you need at least 25% equity for that individual hand to break even. MDF tells you how much of your entire range you must defend as a whole to prevent bluffs from being profitable — it is a range-level calculation. You need both concepts for complete decision-making: use pot odds to evaluate whether a specific hand in your range justifies a call, and use MDF to audit your overall range and ensure you are not over-folding in a given spot. A player can satisfy MDF requirements while making some individual calls that are negative EV — this is the fundamental GTO trade-off between individual hand EV and range balance.
Should you always defend at MDF?
MDF is a floor, not a target. You must defend at least MDF% of your range to prevent bluffs from being immediately profitable, but you can and often should defend more when your range is strong. The critical point is which hands to defend: always prioritize defending the hands with the strongest equity against your opponent's range — your best value hands and bluff-catchers — rather than defending randomly or uniformly. Defending at exactly MDF% with weak hands is worse than defending above MDF% with appropriate hands. In practice, against a solver-balanced opponent you aim to match MDF; against an exploitable opponent who bluffs too much, you defend more; against one who bluffs too little, you defend less. MDF is a diagnostic tool — if you are consistently folding above the maximum fold frequency in a spot, that is a leak.
How does MDF apply preflop in BB defense?
MDF applies directly to big blind defense. Consider a BTN open to 2.5bb with the SB folding — the pot is 3.5bb (2.5bb open + 1bb SB + 0bb BB already posted, but the BB has 1bb invested so the pot facing the BB is 1.5bb already in + 2.5bb open = 4bb total, and the BB must call 1.5bb more). More precisely: BB faces a raise to 2.5bb into a pot of 3.5bb (the 1.5bb from blinds + the 2.5bb open). The BB must call 1.5bb (2.5bb − 1bb already posted). MDF = 1 − 1.5 ÷ (3.5 + 1.5) = 1 − 1.5 ÷ 5 = 1 − 0.30 = 70%. The BB must defend (call + 3-bet) at least 70% of hands against a standard 2.5bb BTN open, or the open becomes a profitable steal with any two cards.
Related Topics
Calculate pot odds and equity for any hand with RiverOdds
Enter your hole cards and board — RiverOdds shows your exact equity and pot odds so you can verify every MDF decision instantly.
Open Calculator →