Poker Probe Bet Chart
How often does a probe bet need to work? This poker probe-bet chart lists folds needed and villain MDF for common sizes — ⅓ through pot — into a $100 pot after the aggressor checked, plus when probing beats checking behind. Pair it with the donk-bet chart, the c-bet chart, the fold equity chart, the MDF chart, and the free bluff calculator.
Probe-bet sizing chart: folds needed and MDF
Setup used for every row: heads-up pot already $100 after the preflop aggressor checked. Action is on you — you bet into them (a probe).
| Probe size (of pot) | Folds a pure probe needs | Villain MDF | Bet into a $100 pot |
|---|---|---|---|
| 33% (⅓) | 25% | 75% | $33 |
| 50% (½) | 33.3% | 66.7% | $50 |
| 67% (⅔) | 40% | 60% | $67 |
| 75% (¾) | 42.9% | 57.1% | $75 |
| 100% (pot) | 50% | 50% | $100 |
Folds needed = bet ÷ (pot + bet). MDF = pot ÷ (pot + bet). They always add to 100%. Numbers assume a pure bluff (zero equity when called) heads-up.
The formula
Folds needed = bet ÷ (pot + bet)
MDF = pot ÷ (pot + bet) = 1 − folds needed
Identical arithmetic to a c-bet or donk of the same size. A half-pot probe still needs one fold in three; a one-third pot stab still needs one in four. What changes is the story: they already declined to bet, so their range is often weaker than when they still had the betting lead.
Worked example: $100 pot, half-pot probe ($50)
They checked. Pot is $100. You bet $50 into them.
- Folds needed (pure): 50 ÷ 150 = 33.3%.
- Villain MDF: 100 ÷ 150 = 66.7%.
- Check: 33.3% + 66.7% = 100%.
Against a nit who folds 40% after checking, a pure half-pot probe clears. Against a sticky checker who almost never folds, you need outs (see the semi-bluff chart) or you should check behind more. Try the calculator preloaded for a $50 turn probe.
Worked example: $100 pot, one-third pot probe (~$33)
Same $100 pot, now a small probe of one-third pot (about $33).
- Folds needed: 33.3 ÷ 133.3 = 25%.
- Villain MDF: 75%.
Small probes after a give-up-looking check only need a quarter of their range to fold, and you put less at risk when called or check-raised. The tradeoff: medium hands and draws continue cheaply — so on wet boards a larger size that denies equity can be better when you do probe.
Probe vs donk vs c-bet
Break-even fold % matches a c-bet or donk of the same size. Timing differs. A donk leads before the aggressor acts. A probe bets after they checked. A c-bet is the aggressor continuing. Probe when their check looks like a surrender, when you want to deny equity, or when checking behind gives a free card you dislike. Otherwise take the free showdown or wait for a clearer street.
The multiway trap
Everyone behind you must fold. Two opponents each folding 40% leave a pure bluff winning only 16% (0.4 × 0.4). A half-pot probe needs 33.3% heads-up — multiway, skip most air probes.
When to probe small vs large
Small (⅓–½). Their check looks weak, heads-up, thin value, or buying cheap folds from missed draws and overcards.
Large (⅔–pot). Wet textures where draws get the right price to a small stab, or polarized value that wants a bigger pot. Pure bluffs at these sizes need 40–50% folds.
Skip the probe. Multiway pots, trap-looking checks from sticky players, no plan versus a check-raise, or when checking behind is clearer. Stack depth after: see the SPR chart.
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See it on Amazon →Probe-bet FAQ
What is a probe bet in poker?
A probe bet is a bet into a player who just checked — often the preflop aggressor who declined to continue. Typical spots: the turn after they check back the flop, or any street where they check to you and you lead to see if they gave up. Unlike a donk bet, the aggressor has already passed the action.
How often does a probe bet need to work as a pure bluff?
Same formula as any bet: folds needed = bet ÷ (pot + bet). A one-third pot probe needs 25% folds; half pot needs 33.3%; two-thirds needs 40%; three-quarters needs 42.9%; pot needs 50%. Equity when called lowers the fold target — see the semi-bluff chart.
How is a probe different from a donk bet?
A donk leads before the aggressor acts. A probe bets after they have already checked. The break-even fold % for the same size is identical; the read is different — their check often means a weaker range than when they still have a bet option.
What is MDF facing a probe bet?
Minimum defense frequency = pot ÷ (pot + bet). Facing a half-pot probe, MDF is 66.7%. Facing a one-third pot stab, MDF is 75%. Fold more often than that and pure probe bluffs print — sticky checkers who never fold still punish light probes.
When should you probe small vs large — or skip?
Small (⅓–½) when their check looks like a give-up and you want cheap folds or thin value. Large (⅔–pot) on wet boards that deny equity to draws, or with polarized value. Skip multiway, when their check is a trap, or when you have no plan versus a check-raise. Pair with the check-raise and donk-bet charts.