This time, I would like to summarize the thinking and points of overbetting.
An overbet is a bet that is larger than the chips in the pot.
In poker, bets that are smaller than the pot size are often used.
However, small bets such as 30% of the pot and oversized bets are increasingly being used.
Overbetting is a play that involves high risk and variance, but it can also be a powerful weapon if used properly.
Let’s take a closer look at overbetting.
◆Expected value of bet◆
When bluffing with an overbet, you might think that the return doesn’t change and the risk only increases.
However, changing the bet size also changes the frequency with which your opponent calls, so you need to think in terms of the expected value of the bet.
Let’s look at an example.
The action continues to the river, the pot is at $100, and
you bluff by betting against a check from your opponent.
① If you bet $50 (half bet), the expected fold rate of your opponent is 40%.
② If you bet $130 (over bet), the expected fold rate of your opponent is 80%.
The expected value of bet ① is
(0.4 * $100) – (0.6 * $50)
$40 – $30 = $10
The expected value of bet ② is
(0.8 * $100) – (0.2 * $130)
$80 – $26 = $54
Assuming the bet amount and opponent’s fold rate in this way, we can see that although both bets have a positive expected value, there is a big difference in the expected value of each bet.
◆Calling Station◆
Players known as calling stations are more interested in drawing or getting a showdown than in the bet size or pot odds, so a value overbet is effective against such players.
Basically, overbets polarize the hand range, so they are usually used with hands close to the nuts or as bluffs, but against such opponents, you can get more value from your opponent by mixing in stronger value hands into your overbets.
◆Changes in bluffing range◆
By overbetting, your opponent’s calling odds will become worse, which will result in them calling less frequently.
If your opponent calls less frequently, you can bluff more frequently, which will increase your bluffing range.
◆Situations where overbetting is effective◆
An overbet is effective when your opponent’s range contains a lot of showdown ranges and there are few traps or air hands close to the nuts.
In such cases, it is effective to put a lot of pressure on your opponent’s range by overbetting, as they may be aiming for a showdown with a check-call.
On the other hand, if your opponent has a lot of air or trap hands in their range, a small bet will be effective.
You can fold with a small bet on air, and if it’s a trap, you can keep your losses small.
Let’s look at some examples of overbetting bluffs and value.
Bluff Example: Head-Jack open-raises, and the Small Hand and Big Hand ( ) call, making it a 3-way flop
. The flop 
is a check-around.
Since the original raiser, Head-Jack, checked, his range is likely to be weak hands below A.
●On the turn 
, SB and BB check, then SB folds in response to HJ’s bet, BB check-raises, and HJ calls
. The betting range for HJ is likely to be one of the marginal ranges mentioned above.
Of course, hands like a slow-played QJ on the flop, a flop set, a set on the turn, or A5s are also possible, but these are rare combinations, and there are many other marginal ranges that are also possible.
Against such a range, the BB is semi-bluffing with a flush draw.
The BB’s value check-raise range is something like QJ, 55, AT, A5, K5, KT, which balances out the semi-bluff range.
The river is a 6, 
and the BB overbet. The river is
a lag, and the BB’s flush draw is not completed, but since the BB has a range advantage and the head and neck’s range is capped, this is a good situation for an overbet bluff, putting a lot of pressure on the head and neck’s capped range.
◇Value example: UTG open-raises, BTN ( ) and BB call, making it a 3-way
. On the flop 
, BB and UTG check, and only BB calls BTN’s bet, making it a HU.
On the turn 
, the BB checks, the BTN bets, and the BB calls.
●On the river 
, the BTN overbet in response to the BB’s check
. The BTN’s 44 was a set on the flop and a full house on the turn.
The important thing here is that the BTN’s 44 did not block the BTN’s range to aim for value against the BB.
The BB’s range includes draws as well as many 9x and 8x ranges.
Against such a range, the BTN’s overbet to aim for maximum value is a more profitable play.
