GGPOKER

Fold too much, and you’re letting your opponent print money. Math tells you exactly how much is too much.

Every time your opponent bets, they’re making a play that could be a bluff. If you fold too often, their bluffs become automatically profitable. Your opponent doesn’t even need good hands to win pots. Minimum Defense Frequency (MDF) is the mathematical concept that tells you exactly how often you need to continue to prevent this exploitation.

This guide explains MDF from first principles, shows you how to calculate it, and helps you apply it correctly at the tables.

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Understanding the Core Concept

MDF answers a fundamental question: How often must I continue (call or raise) to make my opponent’s bluffs break even?

If you defend at exactly MDF, your opponent’s bluffs win $0 in expected value. If you defend more, their bluffs lose money. If you defend less, their bluffs profit.

Why This Matters

Imagine if your opponent could bluff with any two cards and show an automatic profit because you fold too much. They’d bluff constantly, and they’d be correct to do so. MDF prevents this by ensuring you defend often enough to punish bluffs.

The Basic Formula

MDF is calculated as:

MDF = Pot size / (Pot size + Bet size)

Or equivalently:

MDF = 1 – (Bet size / (Pot size + Bet size))

Let’s calculate MDF for common bet sizes:

Bet Size	MDF	Max Fold Frequency
1/4 pot	80%	20%
1/3 pot	75%	25%
1/2 pot	67%	33%
2/3 pot	60%	40%
3/4 pot	57%	43%
Pot	50%	50%
1.5x pot	40%	60%
2x pot	33%	67%

Against a pot-sized bet, you need to continue with at least 50% of your range to prevent automatic bluff profits. Against a half-pot bet, you need to continue with 67%.

 

Applying MDF: A Worked Example

Let’s trace through a hand to see MDF in action.

Situation: You raised preflop from the cutoff with a standard range. Big blind called. Pot is $20.

Flop: K♠ 8♦ 3♣

You c-bet $13 (65% pot). Opponent calls. Pot is now $46.

Turn: 5♥

You bet $30 (65% pot). Opponent calls. Pot is now $106.

River: 2♠

You bet $75 (about 70% pot).

Opponent’s MDF calculation:

MDF = 106 / (106 + 75) = 106 / 181 = 58.6%

Your opponent needs to continue with approximately 59% of their range to prevent your bluffs from being automatically profitable.

If they’re only calling with top pair or better, they’re likely defending too little. If they’re calling with any pair, they might be defending close to correct.

The Flop-Turn-River Chain

MDF applies at each street, and the frequencies compound. This is crucial for understanding multi-street situations.

Compound Folding

If your opponent bets three streets and you need to defend at these frequencies:

• Flop: 60% (fold 40%)
• Turn: 60% (fold 40%)
• River: 60% (fold 40%)

Your total continuing frequency from flop to showdown:

0.60 × 0.60 × 0.60 = 21.6%

You’re only getting to showdown with about 22% of your flop range! This is why calling ranges need to be constructed carefully, because you’re defending a progressively smaller portion of your range each street.

Implications for Range Construction

When you call flop, you’re committing to potentially calling turn and river. Your flop calling range should contain:

• Hands strong enough to call multiple streets
• Draws that improve to strong hands
• Some hands that become bluff catchers on later streets

Calling flop with hands that fold to any turn pressure is a leak. Don’t put money in that you’ll likely abandon.

When MDF Doesn’t Apply Perfectly

MDF is a theoretical baseline, not a commandment. Several factors modify how you should apply it:

Your Range Is Capped

If your range is capped, you might need to over-defend with medium-strength hands or accept that your opponent can profitably bluff you.

Example: You called preflop and post-flop. Your range is capped (no sets, probably less than top two pair). Against a turn overbet, you might have no choice but to fold more than MDF suggests.

Opponent Doesn’t Bluff Enough

MDF prevents bluff exploitation, but if your opponent never bluffs, defending at MDF is leaving money on the table. You should fold more.

Against recreational players who only bet for value, ignore MDF and fold your bluff catchers.

Board Texture Favors Opponent

When the board heavily favors your opponent’s range, their betting range contains more value and fewer bluffs. You can fold more than MDF suggests.

Example: You defend BB with J♦9♦ against button open. Board: A♠ A♥ K♣ Q♦ 5♠.

Button’s range contains many aces, kings, and queens. Your jack-high has no showdown value, and their bluff frequency is naturally low. Fold despite what MDF might suggest.

You Have Showdown Value

MDF calculations assume your hand has no independent value. If your hand might win at showdown unimproved, that equity adds to your calling decision.

A hand with some showdown value (like third pair) might call even if pure MDF math suggests folding.

MDF vs. Pot Odds

MDF and pot odds are related but different concepts:

Pot Odds

Pot odds tell you how often you need to win to break even on a call. If you’re getting 2:1, you need to win 33% of the time.

MDF

MDF tells you how often you need to continue to prevent opponents’ bluffs from being automatically profitable. It’s about your overall defense frequency, not any single hand’s equity.

How They Connect

When deciding whether to call with a specific hand:

• Use pot odds to determine if THIS hand should call
• Use MDF to ensure your OVERALL range calls often enough

You might fold some hands with enough equity to call (they’re at the bottom of your range) and call some hands with less equity (they serve as bluff catchers in your overall strategy).

Constructing MDF Ranges

Here’s how to build ranges that defend at approximately correct frequencies:

Step 1: Identify Your Range

Determine what hands you have in the given situation. On the river after calling flop and turn, what’s in your range?

Step 2: Calculate Required Defenses

Based on the opponent’s bet size, calculate MDF. If they bet 75% pot, you need to defend approximately 57%.

Step 3: Order Your Hands by Strength

Rank your hands from strongest to weakest. Strong hands clearly call. Weak hands clearly fold. The question is where to draw the line.

Step 4: Find the Cutoff Point

Call with the top X% of your range where X = MDF. Everything below that threshold folds.

Step 5: Adjust for Specifics

Consider blockers, opponent tendencies, and board texture. Some hands slightly below the threshold become calls (good blockers to an opponent’s value). 

MDF in Practice: GGPoker Application

Here’s how to apply MDF concepts during actual play:

Against Unknown Opponents

Default to roughly MDF-compliant defense frequencies. This protects you from exploitation while you gather information.

Against Aggressive Players

Players who bet frequently might be bluffing more than GTO suggests. Defend slightly more than MDF to punish their aggression.

Use GGPoker’s Smart HUD to aid in finding these players. High aggression factors indicate potential over-bluffing.

Against Passive Players

Passive players who suddenly bet are rarely bluffing. Defend less than MDF and fold your bluff catchers.

Using PokerCraft

Review your defense frequencies in common spots:

• Are you folding more than 50% to pot-sized bets?
• Are you folding more than 40% to 2/3 pot bets?

If so, you might be over-folding and can tighten up your folding range.

Common MDF Mistakes

Applying MDF Blindly

MDF is a guideline, not a rule. Blindly calling at MDF against opponents who never bluff will lose you money.

Ignoring Range Disadvantage

When your range is significantly weaker than your opponent’s, MDF math doesn’t capture the full picture. You may need to over-fold in some spots against these players.

Not Accounting for Multi-Street Defense

Calling the flop at MDF only to fold the turn to any bet is not the correct overall defense. Plan for multiple streets.

Defending with Wrong Hands

Reaching MDF by calling with bad bluff catchers while folding better hands is a mistake. Call with your best bluff catchers, not your worst.

Over-Defending Low Cards

On high boards like A-K-Q, your low cards have reduced value. MDF might suggest 60% defense, but if 70% of your range is low pairs that can’t beat anything, you may need to accept some exploitation.

MDF and Bet Sizing Strategy

Understanding MDF helps you size your own bets effectively:

Smaller Bets Require More Defense

A 1/3 pot bet only needs your opponent to fold 25% of the time. Use small sizing when you want calls (value hands) or when your range is weak.

Larger Bets Allow More Folding

A pot-sized bet only needs 50% defense. Use larger sizing when you have polarized ranges or want to put maximum pressure on your opponent.

Overbets Create Extreme Pressure

A 2x pot bet only requires 33% defense. Your opponent can fold two-thirds of their range and still be unexploitable. Use overbets when you have the nuts or air and want maximum fold equity.

Key Takeaways

• MDF = Pot / (Pot + Bet): This tells you the minimum defense frequency
• Smaller bets require more defense: You shouldn’t fold as much against small bets
• MDF is a baseline, not a rule: Adjust for opponent tendencies and range interactions
• Plan for multiple streets: Defense frequencies compound. You reach showdown with a small fraction of your flop range
• Over-folding is exploitable: If you fold more than MDF, your opponent’s bluffs essentially print money
• Call with best bluff catchers: Reach MDF with your strongest medium hands, not your weakest

Defend Correctly

MDF provides a mathematical foundation for defending against bets. Memorize the key numbers: 67% defense against half-pot, 50% against pot-sized bets. These serve as your starting point.

Then adjust. Against aggressive players, defend more. Against passive players, defend less. Against capped boards, accept some exploitation. Against completed draws, tighten up.

The goal isn’t to hit MDF exactly every time—it’s to understand the math well enough to make informed deviations. When you know how often you “should” be calling, you can make better decisions about when to call more or less.

Review your defense frequencies in PokerCraft. Find spots where you’re over-folding or over-calling. Adjust your ranges to approach correct frequencies while accounting for opponent tendencies.

Math protects you from exploitation. Learn it, apply it, and profit from it.