Thin value

In this lesson

• Find river bets that beat enough of the hands that call.
• Size thin value bets small.
• Recognise when the risk of a raise turns a thin bet into a losing one.
• Bet thinner against passive players and less thin against frequent raisers.
• Stop checking back strong hands that should bet.

Read first: The river: value, bluffs and the middle · Advice, not a lock: every lesson opens.

Concepts used: Thin value betting, Bet sizing and polarisation

What thin means

A thin value bet is one that wins only a little more than half the time it is called. It is worth making, because a little edge on every call adds up, and missing it is a quiet leak: checking back a hand that would have been paid shows up in no single hand as a loss.

Count it. You bet 7 bb into 20 bb with a top pair. The opponent calls 60% of the time and you are ahead of 60% of the calls. Per call you win 7 bb six times in ten and lose it four: 0.6 − 0.4 = 0.2 of the bet, 1.4 bb. Called 60% of the time, that is 0.6 × 1.4 = 0.84 bb per bet over checking.

Size it small

The thinner the value, the smaller the bet. A small bet is called by more of the hands you beat, and costs less when it runs into better. Rail's solves agree: in position after a check its top pairs bet about half the time, and the small size is a far larger share of their bets than of its strongest hands'; out of position, as the first to act, it bets its top pairs mostly small.

When a raise makes it too thin

Every raise you must fold to costs the bet. If the opponent in the example also raises 5% of the time and you fold, each raise costs at least the 7 bb: 0.05 × 7 = 0.35 bb, which leaves 0.84 − 0.35 = 0.49 bb. Raise more often, or call more rarely, and the thin bet turns into a loss.

That is why thin value goes thinner against passive players and less thin against players who raise the river: the same hand is a bet against one and a check against the other.

River solves on demand: the charts' ranges narrowed on the flop and turn by Rail's heuristic model, with bets of 33%, 75% and 150% of the pot and all-in. The drills deal hands where Rail's solve mixes, which is where thin value lives.

Rules of thumb

• Bet whenever you win more than half the times you are called, even by a little.
• Thin value bets small.
• Every raise you must fold to costs the whole bet: count it.
• Do not check back a strong hand that would be paid.

When they break

• Against a passive caller, bet thinner and a little bigger.
• Against a frequent river raiser, check more of your thinnest bets.

Example hands

Practice

The lesson is mastered when every exercise below that Rail can grade is passed. Missed items come back later as review cards.