MDF Calculator — Minimum Defense Frequency
Pot and bet in — how much of your range must continue, and how often their bluffs need to work
Enter Values
Chips, dollars, or big blinds — units cancel out
That is a 66% pot bet
Common sizings (exact fractions)
| Bet size | MDF | Bluffs must work |
|---|---|---|
| 25% pot | 80.0% | 20.0% |
| 33% pot | 75.0% | 25.0% |
| 50% pot | 66.7% | 33.3% |
| 66% pot | 60.0% | 40.0% |
| 75% pot | 57.1% | 42.9% |
| 100% pot | 50.0% | 50.0% |
| 150% pot | 40.0% | 60.0% |
If you fold more than 39.8% of the time in this spot, betting 66 into 100 with any two cards is instantly profitable for your opponent.
A pure bluff of 66 into 100 risks 66 to win 100, so it needs folds 39.8% of the time to break even — more folds than that and the bluff prints.
Micro-stakes reality check
MDF is the ceiling vs a balanced opponent. Most micro-stakes players under-bluff turns, rivers, and raises — folding more than MDF against those lines is not a leak, it is the exploit. See the guide below for when each mode applies.
Guide
Minimum Defense Frequency, explained
What MDF actually means
When someone bets, they are laying themselves a price. A bet of 66 into a pot of 100 risks 66 to win 100, so a pure bluff breaks even when you fold 66 ÷ (100 + 66) = 39.8% of the time — that number is alpha. Flip it around and you get the Minimum Defense Frequency: the share of your range that must continue so their any-two-cards bluff does not automatically profit — MDF = pot ÷ (pot + bet), which for that 66% pot bet is 60.2% (exactly 60% for a true two-thirds-pot bet). MDF + alpha always sum to 100%.
Note what MDF does not say: it does not tell you which hands to continue with, or that any specific call is profitable. It is a range-level tripwire — fold beyond it against a balanced opponent and you become the profit source.
MDF vs pot odds
The two formulas look similar and answer opposite questions. Pot odds — bet ÷ (pot + 2×bet)for a call — is the caller's single-hand question: does this hand have enough equity? MDF is the defender's range question: am I folding so much that bluffing me is free money? Facing that 66-into-100 bet, a call needs about 28% equity (66 ÷ 232), while your overall range must defend ~60%. Use our pot odds calculator for the first number; this page gives you the second.
When to deviate at micro stakes (honest version)
MDF is unexploitable, not maximally profitable. It only binds when your opponent actually bluffs at equilibrium frequency — and micro-stakes populations do not:
- → Over-fold without guilt vs river bets, check-raises, and turn barrels from passive players. Those lines are value-heavy in real populations; hitting "full MDF" there means paying off two pair over and over.
- → Defend closer to MDF vs small flop c-bets (25-33% pot, where MDF is a demanding 75-80%) and vs aggressive regulars who actually find bluffs. This is where mass folding gets punished.
- → Use alpha on offense. Before bluffing, ask whether this specific player folds more than the break-even number. A 150% pot overbet needs 60% folds — most micro-stakes callers simply do not fold that often with a pair.
One more practical note: MDF assumes the bluffs have zero equity when called. Real bluffs usually have outs, so bettors can profitably bluff a bit more than the raw numbers suggest — another reason MDF is a compass, not a law. To see what your range actually holds when the bet comes, run the same spot through our range explorer, and for full-range strategy checks try solver-lite.
Frequently asked questions
What is the MDF formula?
MDF = pot ÷ (pot + bet). Facing a two-thirds-pot bet, that is 1 ÷ (1 + 0.667) = 60%: you should continue (call or raise) with 60% of your range and can fold at most 40%. Against a pot-sized bet the MDF is 50%, and against a half-pot bet it is 66.7%.
What is alpha (the bluff break-even)?
Alpha = bet ÷ (pot + bet) — the share of the time a pure bluff must work to break even. It is exactly 1 − MDF. A two-thirds-pot bluff risks 0.667 units to win 1, so it needs folds 40% of the time. If your opponent folds more often than alpha, their range is exploitable by bluffing; if they fold less, pure bluffs lose money.
What is the difference between MDF and pot odds?
Pot odds answer a one-hand question: given this price, does MY hand have enough equity to call? MDF answers a range question: how much of my WHOLE range must continue so a bettor can't profit by bluffing any two cards? Use pot odds to decide individual calls; use MDF to check whether you are folding so much overall that you have become a bluffing target.
Should I always defend the full MDF at micro stakes?
No — and pretending otherwise would be bad advice. MDF is the unexploitable ceiling against an opponent who bluffs at the correct frequency. Micro-stakes populations under-bluff badly, especially on turns and rivers and against check-raises, so folding more than MDF against those lines simply wins money. Treat MDF as a diagnostic: if you are miles below it against small flop c-bets (where people do bluff), you are over-folding; if you defend the full MDF against a passive player's river jam, you are paying off value hands.
Does MDF apply to raises and multiway pots?
The same risk/reward logic generalizes to raises: the raiser risks their raise amount to win pot + your bet, so the break-even fold rate is risk ÷ (risk + reward), and your defense requirement adjusts accordingly. In multiway pots the defense burden is shared — no single player must defend the full MDF, which is one reason bluffing into several opponents needs a much better reason than bluffing into one.
Related tools
The caller's side of the same math — break-even equity per hand.
See which parts of your range can actually defend on a given flop.
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Want the full poker-math foundation? Our free 15-minute Poker 101 course covers equity, pot odds, and defense frequencies from zero.
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