Minimum Defense Frequency: the math behind "you're folding too much"
Most trackers that flag "you fold too much to c-bets" compare your fold rate to the population average. That tells you what everyone else does, good or bad — it doesn't tell you the one thing that's actually true regardless of population: the maximum frequency it is ever mathematically correct to fold against a given bet size.
That number has a name — Minimum Defense Frequency — and the formula behind it is short enough to use at the table.
The formula
MDF = pot / (pot + bet)
MDF is the fraction of your range you need to continue (call or
raise) so that betting any two cards stops being automatically
profitable for your opponent. Fold more than 1 − MDF of the
time, and a bet with zero equity shows an instant profit no matter what
it's holding.
A worked example
Say the pot is 10bb and you face a 5bb bet. MDF = 10 / (10 + 5) = 66.7%. You need to continue at least two-thirds of your range here — if you're folding more than a third, a pure bluff is printing money against you regardless of what your opponent is actually holding.
Double the bet size to a full pot-sized 10bb bet, and the math moves the other way: MDF = 10 / (10 + 10) = 50%. Bigger bets buy the bettor a higher fold-equity ceiling — which is exactly why MDF has to be computed per bet size, not quoted as one flat number for "facing a c-bet."
Why this beats a population-average target
A population comparison answers "am I folding more than other people." MDF answers "am I folding more than is ever correct, given the actual size of this exact bet." The first is a social benchmark. The second is a hard ceiling derived from the pot itself — it doesn't care what anyone else at the table does, and it's computed fresh from the real bet and pot size in front of you rather than guessed or averaged from a database of other people's hands.
It's also a one-sided check by nature: MDF only ever tells you the most you can afford to fold. It has nothing to say about folding too little — that's a different, separate leak with a different diagnosis.
Where this is headed
This is exactly the kind of number a leak-finder should be checking your real fold rate against — not a population percentage, a hard pot-odds ceiling computed from your own actual bet sizing. It's the benchmark we're building the next round of postflop leak checks around, and we'll have more to say once it ships.