Minimum Defense Frequency

Minimum Defense Frequency (MDF) answers a narrower question than "should I call this specific hand": given a bet size, what fraction of your whole range must continue (call or raise) so that the bettor can't print money by bluffing with 100% of their bluffing combos? The formula is MDF = pot / (pot + bet) — the same pot-odds ratio from the previous topic, just applied to a range instead of one hand.

Its complement, 1 − MDF = bet / (pot + bet), is the bettor's breakeven fold equity: how often the defender must fold for a zero-value bluff to profit. Small bets need few folds (a half-pot bet only ~33%); overbets need many (a pot-sized bet 50%, a 2×-pot overbet 67%). That asymmetry is why bet sizing and bluff frequency are linked — the How this app grades you page shows how the postflop range-narrowing model uses these thresholds.

Two things MDF is not. It isn't "call with your top X% of hands" — defending can be a call or a raise, and the combos you keep should be your best bluff-catchers, not an arbitrary top slice. And it isn't a number to hit exactly: it's a ceiling on how exploitable over-folding is, not a target divorced from hand strength.

Drag the bet-size slider below to see how MDF and the bettor's breakeven fold equity move together.

MDF vs. bet size

MDF (defender must continue)57.1%
Bettor's breakeven fold equity42.9%

MDF = pot / (pot + bet) = 10 / (10 + 7.5) = 57.1%

If the defender folds more often than 42.9% of the time, a bettor who fires this size with any two cards shows a guaranteed profit — a pure bluff wins the pot every time it isn't called. Defending at least the MDF fraction (with bluff-catchers, not necessarily the whole range) removes that free-roll and forces the bettor back to betting for value.

Three honest caveats from this app's own grader: it assumes defenders over-defend tiny bets (below half pot), so a min-bet bluff never shows the free profit this formula alone would suggest; in multiway pots the chance everyone folds shrinks multiplicatively with each extra live player, so a pure multiway bluff grades strictly losing — more players, less fold-through; and the breakeven above is the pure-bluff number under fold-or-call — in real grades your bet also carries a raise-risk branch (part of what continues can raise you), which strips some of the equity credit a non-bluff bet books when called, so an equity-carrying bet needs somewhat more folds than plain fold-or-call pricing suggests (never more than the pure-bluff ceiling above — a bluff has no equity credit left to strip).