Minimum defence frequency (MDF): how often you have to call

Minimum defence frequency is the share of your range you must continue with against a bet so that a bluff with any two cards cannot profit, and it equals pot divided by pot plus bet. Facing a half-pot bet you must defend about two-thirds of your range; facing a pot-sized bet, exactly half. Defend more than the number and bluffs are not automatically profitable; defend less and any two cards beat you. Here is where the number comes from and where it stops applying.

What minimum defence frequency means

When someone bets, they are offering you a price to fold. If you fold too often, a bluff with the worst hand at the table still profits, because it wins the pot more than often enough to cover the times it gets called.

MDF is the threshold that shuts that down. It is the fraction of your range you must continue with, by calling or raising, so the bettor cannot show a profit by bluffing every time. It is a statement about your whole range, not any single hand. You are not asking "is my hand good enough"; you are asking "am I continuing with enough of my range overall".

The formula and a worked example

The formula is short:

MDF = pot / (pot + bet)

That is the pot before the bet, divided by the pot after the bet is called. Work through the common sizes:

• Half-pot bet. Pot is 100, bet is 50. MDF = 100 / 150, about 67 percent. You must continue with two-thirds of your range and may fold one-third.
• Three-quarter-pot bet. Pot is 100, bet is 75. MDF = 100 / 175, about 57 percent. You fold a little over two-fifths.
• Pot-sized bet. Pot is 100, bet is 100. MDF = 100 / 200, 50 percent. You defend half.
• Overbet, twice the pot. Pot is 100, bet is 200. MDF = 100 / 300, about 33 percent. You can fold two-thirds.

The pattern is the heart of it: the smaller the bet, the more of your range you must defend, because the bluff is risking less to win the same pot. The bigger the bet, the more you are allowed to fold.

Why MDF exists at all

MDF is the defender's mirror of a bettor's balance. A bettor who bluffs the right amount makes you indifferent to calling with your marginal hands. MDF is the matching constraint on your side: defend the right amount and you make the bettor indifferent to bluffing.

If both players hit their numbers, neither can exploit the other, which is what a GTO baseline looks like in a single betting decision. The same indifference logic is what the open-source DCFR solver behind this site's charts converges on when it solves a spot. MDF is one of the cleanest places to see game theory show up at the table, because it turns "do not fold too much" into an exact percentage.

MDF versus pot odds: two sides of the same bet

MDF and pot odds describe the same bet from opposite seats, and mixing them up is common.

• Pot odds are about one hand. They tell the caller what equity a specific holding needs to call profitably. Facing a half-pot bet, you need about 25 percent equity to call.
• MDF is about the whole range. It tells the defender what share of all their hands must continue so the bettor cannot bluff profitably.

A useful way to hold both: pot odds decide whether this hand continues; MDF checks whether enough of your hands continue in total. You use pot odds to pick which hands defend, and MDF to confirm you are not over-folding as a range. The pot odds page lets you plug in a size and see the equity threshold directly.

MDF protects your range from bluffs; pot odds protect your hand from a bad call. You need both, because a range that defends the right amount can still defend with the wrong hands.

Where MDF breaks down in practice

MDF assumes the bettor bluffs optimally. Most opponents do not, and that is where pure MDF will cost you money.

• Against players who rarely bluff, defending to MDF is a leak. If they almost never fire without a real hand, you should fold more than MDF says and let the bluffs they are not making go uncollected.
• Against players who bluff too much, MDF is a floor, not a ceiling. Defend wider than the formula, because their over-bluffing makes more of your bluff-catchers profitable.
• Deep multiway or with strong draws, raw MDF gets fuzzy, because the value of continuing is not only about preventing bluffs but about the equity your hand realises later.

This is the same lesson as GTO versus exploitative play: MDF is the unexploitable baseline, and you deviate from it on purpose when a read tells you to. Use it as the default when you have no information, then bend it when you do.

Bottom line

Minimum defence frequency is the share of your range you must keep continuing against a bet so the bettor cannot profit by bluffing any two cards, and it equals pot divided by pot plus bet. Smaller bets force wider defence; bigger bets let you fold more. It is the range-level mirror of pot odds, which work at the level of a single hand. Treat MDF as your baseline against unknown opponents, use pot odds to choose which hands fill the quota, and step away from the number deliberately against players who bluff too little or too much. Defend enough that no bluff is free, and no more.