MDF in Poker – Why You Need to Understand Minimum Defense Frequency

The way professional players think about the game of poker has changed dramatically over the recent years, with game theory optimal (GTO) concepts now used as the new strategy baseline by most serious players.

Minimum defense frequency is one such concept, which signifies the minimum portion of your range you should be calling (or raising) when facing bets to keep your opponents from exploiting you by bluffing.

MDF, as it is often referred to, is a fairly advanced concept that you will hardly be able to apply in play but that you will be able to work with while practicing your ranges using poker tools like PIO solver.

If you want to play higher-stakes poker and face very tough competition, you will need to understand poker MDF and practice this concept while studying to ensure you don't get exploited by the best players out there.

However, we are also going to teach you how you can play against most random players in lower to mid-stakes games, avoid having to learn too much about minimum defense frequency, and apply the concept of pot odds alone to still remain profitable.

Let's jump into it by talking about how MDF works, when you can use it and why it is useful when playing against knowledgeable opponents.

How to Use Minimum Defense Frequency in Poker

The idea of minimum defense frequency is one that can only make sense to poker players who think about the game in terms of ranges. If you are playing poker the right way, you should be pretty clear about the range of hands you can have in any given situation and all the hands that range is made up of.

Minimum defense frequency is the number that tells us what percentage of our entire range we should continue with when facing a bet from our opponents in a poker hand.

To calculate MDF in poker, you can use this simple formula:

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

For example:

MDF = 100 / (100+50)

MDF = 100 / 150

MDF = 0.67

To get your MDF percentage, all you need to do is multiply this number by 100. In this case, you should play 67% of your range, which is always the case when facing a half-pot bet.

Once you calculate your poker MDF, you will work with a solver to determine which hands fall into that 67% category and which hands would be best to call when facing this bet.

Out of all your hands, you will select the ones that unblock the most possible bluffs that your opponent could have, along with the strongest hands in your range, such as the absolute nuts.

By practicing with solvers in this way, you will gradually learn how to bluff-catch profitably against balanced ranges, which will give you a great idea of when to make calls when facing actual bets in real games.

Here is a quick rundown of what your MDF should be when facing various common bet sizes in poker:

When to Use Minimum Defense Frequency

Now you know how to calculate MDF in poker, but the question still remains when exactly you should use it and whether or not it will increase your long-term profit.

The truth is that you can’t actually figure out which hands in your range you should call and which you should fold perfectly while playing a hand, as there is simply not enough time, and doing it without a solver would take forever.

Instead, you can practice using MDF during your studying hours and then make good educated guesses as to which hands to call and which to fold while playing.

For example, if you happen to be in a situation where your MDF is 50%, you should automatically know which hands are at the top of your range and which are at the bottom, which should make it easy to find the definitive call and fold candidates.

In between those two, you should think about all the hands you still have in your range and split them approximately between those you want to call and those you want to fold.

Also, note that the solver likes to use mixed call/fold/raise strategies with many hands, but such strategies are nearly impossible to apply by human players. For that reason, you should usually either fold or call certain hands in certain spots and simplify the strategy as much as you can.

When playing against very strong and balanced opponents, you should use MDF as your baseline for making calls or folding hands against bets.

Players who play a balanced strategy will have a range that includes both bluffs and value hands in all situations but may end up playing exploitatively against you if they realize you are deviating from MDF.

However, against many other players, using minimum defense frequency might actually end up costing you money, as using a more exploitative approach to the situation could be more profitable.

When to Deviate from MDF in Poker

We have learned that thinking in terms of MDF when facing bets from balanced players is a good idea, but there are definitely many situations in which you will not want to stick to this concept too tightly.

In real poker games, most players will not be completely balanced, and their imbalance will usually make it so that their ranges don’t contain enough bluffs.

Specifically, there are many boards on which your opponent will not have many natural bluffs to continue with on the river, which will cause their turn and river bets to be more value-heavy than they should be in theory.

In fact, the vast majority of players under bluff in most situations, which means you can usually deviate from MDF and call bets tighter against the population.

However, you should also note that there are some wild players who will keep bluffing very often regardless of the board texture and their particular hand, in which case you should be calling more than the MDF suggests.

By playing an exploitative strategy against your average poker player and deviating from MDF and GTO, you will be printing more equity than you ever could by using these concepts.

Using Pot Odds When Facing a Bet

While MDF has a very important place in poker strategy, especially for heads-up poker and in other game formats against very strong players, you won't always have to use it when facing your average opponent.

A much simpler way to play when facing bets is to look at your pot odds, estimate your opponent’s range, and make a decision on whether your hand has enough equity to call against that range.

Instead of having to figure out your MDF and playing a mixed strategy with various hands, you can simply always fold or always call with hands that do or don’t have enough equity when facing a bet.

In order to calculate your Pot Odds, you will use the following formula:

Pot Odds = Bet Size / (Pot Size + Bet Size + Call Size)

Pot Odds = 50 / (100 + 50 + 50)

Pot Odds = 50 / 200

Pot Odds = 0.25

You will need to multiply this final number by 100 to get a percentage, in this case, 25%. So, facing a 50% pot-sized bet, you must have 25% equity against your opponent's range to make the call profitable.

What that means is that you will be able to call with a lot of bluff catchers on boards where your opponent can have many bluffs or call less frequently in spots where your opponent often has a value hand.

Again, it would be difficult to apply this simplified strategy against a well-balanced range, but facing an average opponent who either under bluffs or over bluffs significantly, you can easily get away with using pot odds as your main guideline instead of MDF.

Conclusion on MDF in Poker

Minimum defense frequency has emerged as a popular concept from the GTO perspective but is one that you won't necessarily have to apply in your game unless you are playing against very high-level players.

While MDF is almost obligatory when playing poker against other players whose strategy is based on GTO models, you can get around using it when facing an average poker player.

Yet, learning more about MDF and practicing with this concept in your solver will help you better understand what types of hands make for good bluff catchers on various boards and just how often you should be calling against good players who are capable of bluffs on all board textures.

Even though you won't be calculating MDF on the spot while playing poker, getting a good grasp on it will make you a better poker player and help your game significantly in the long run.

As you learn more about MDF, make sure to get your pot odds down very well also, and remember to always calculate your pot odds when facing bets and use this concept more often against recreational players or regulars at lower levels.

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