MDF: The Minimum Defense Frequency to Deny Profitable Bluffs

How often must you call to prevent your opponent's bluffs from being automatically profitable? Learn the principles of MDF and when to deviate from it.

What Is MDF?

Every time your opponent bets and you fold, they can profit by bluffing with any hand. The minimum frequency at which you must defend to prevent this is called MDF (Minimum Defense Frequency).

MDF by Bet Size

Bet Size	MDF	Folding Allowed
33% pot	75%	Up to 25%
50% pot	67%	Up to 33%
75% pot	57%	Up to 43%
100% pot	50%	Up to 50%
150% pot	40%	Up to 60%

Practical Example: Applying MDF

Applying MDF on the River1/2

Hero (BB)

riverPot 40

Villain bets 30 (75% pot)

Analysis

MDF = 40 / (40 + 30) = 57%

Hero must call with the top 57% of their range

A♥T♠ = ace high. Does it fall within the top 57%?

Depends on Villain's bluff frequency — default is to follow MDF and call

4 Situations Where You Should Ignore MDF

MDF is built on the assumption that "the opponent bluffs optimally." When this assumption breaks down, you don't need to follow MDF.

1. When the Opponent Rarely Bluffs

If a tight player at a live low-stakes game makes a big river bet, it's almost always value.

2. Facing a Flop C-Bet OOP

Applying MDF to a flop c-bet while OOP leads to calling with too many weak hands. Since OOP equity realization is below 100%, folding more than MDF dictates is correct.

3. When the Opponent's Bluffs Have Equity

MDF is calculated assuming "zero-equity bluffs." In practice, bluffs often hold some equity through draws or high cards. In these cases, you can defend slightly less without making their bluffs automatically profitable.

4. Multiway Pots

In pots with three or more players, the defense burden is shared. You don't need to meet MDF on your own.

MDF vs Pot Odds: Which One Should You Use?

Concept	Perspective	When to Use
Pot Odds	Hand-specific	"Is calling profitable with this hand?"
MDF	Range-wide	"What percentage of my range should I call with?"

Source: Upswing Poker, GTO Wizard Blog