ConceptsBetting
Bet sizing and polarisation
Small, big or overbet: every size has a job, and the job depends on the board and on which hands you bet.
What it is
Small bets (about a quarter to two fifths of the pot) charge many hands a little. They suit ranges with a broad advantage on boards that do not change much: most of the range can bet, and most of the opponent's range can still call.
Big bets (two thirds to a full pot) and overbets (more than the pot) suit polarised ranges — very strong hands and bluffs, no middle — and need a nut advantage behind them. They deny equity on boards where it is running, and they charge the most to the hands that call.
A polarised range bets its best hands and its bluffs and checks its medium hands. A merged (linear) range bets from the top down, including medium hands that are ahead of what calls, usually with a smaller size.
Why it matters
Size decides who can call, how much equity you deny, and how many bluffs your value can carry. On the river, with a perfectly polarised range, a bet can contain bet / (pot + 2·bet) bluffs and still leave the bluff-catcher indifferent.
Picking size by hand strength alone — big with strong hands, small with weak ones — tells an attentive opponent exactly what you have. Size by range: decide what the bet is for, then put every hand with that purpose into it.
The maths
The bluff share of a polarised river bet equals the bet divided by the pot plus twice the bet.
Value combos per bluff combo equal the pot plus the bet, divided by the bet.
| Bet | Alpha | MDF | Caller needs |
|---|---|---|---|
| 25% | 20% | 80% | 16.7% |
| 33% | 24.8% | 75.2% | 19.9% |
| 50% | 33.3% | 66.7% | 25% |
| 75% | 42.9% | 57.1% | 30% |
| 100% | 50% | 50% | 33.3% |
| 150% | 60% | 40% | 37.5% |
| 200% | 66.7% | 33.3% | 40% |
Worked example
Three river sizes into a 10 bb pot
A perfectly polarised river range: the nuts and air, nothing in between.
- Half pot, 5 bb: bluffs can be 5 / (10 + 10) = 25% of the bets — 3 value hands per bluff.
- Pot, 10 bb: 10 / 30 ≈ 33% bluffs — 2 value hands per bluff.
- Double pot, 20 bb: 20 / 50 = 40% bluffs — 1.5 value hands per bluff.
Bigger bets carry more bluffs per value hand, but they need enough nutted hands to be worth making. With few nuts, a smaller size lets you bet more often.
Try it
Set a pot and a bet: the calculator shows the bluff share and value-per-bluff ratio for a polarised bet of that size.
Common mistakes
- Betting big with strong hands and small with weak ones.
- Overbetting without a nut advantage.
- Betting small on dynamic boards, which lets draws in cheaply.
- Betting medium hands big into ranges that only continue with better.
In your hands
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Related concepts
- MDF and alphaMDF is how much of your range has to continue against a bet; alpha is how often that bet must make you fold.
- Nut advantageWho holds more of the very strongest hands on this board — which decides who can bet big.
- Thin value bettingBetting a hand that is only a little ahead of what calls it — profitable more often than it feels.