Over/Under 13, and the Bet Casinos Had to Withdraw
Updated
You bet whether your first two cards total more or less than 13, with an ace counting one. Exactly 13 loses both ways — that is where the house edge lives. It is also the side bet that proved side bets can be beaten, which is why you rarely see it now.
- Over 13: house keeps 6.55%. Under 13: 10.07%.
- Exactly 13 loses both bets. It happens 8.3% of the time.
- The ace counts as 1, not 11. That is what makes Under playable at all.
- Highly countable — and that is why it was pulled from most floors.
How the two bets differ
Six decks, ace counting as one, both bets paying even money and losing on exactly 13.
| Bet | Wins | Loses | House edge |
|---|---|---|---|
| Over 13 | 46.7% | 53.3% | 6.55% |
| Under 13 | 45.0% | 55.0% | 10.07% |
Both match the published figures. The asymmetry comes from ten-value cards: there are sixteen of them per deck, so totals above 13 are simply more common.
The bet that got counted out of existence
Over/Under 13 has an unusual place in blackjack history. Because it depends only on the two cards you are dealt, and because the shoe’s composition shifts as cards leave, a player tracking high and low cards could tell when Over or Under had turned profitable — and the swings were large enough to be worth acting on.
It became one of the most reliably beatable bets a casino ever put on a blackjack layout, and it was withdrawn from most floors. When you do meet it, it is usually with a continuous shuffler that resets the shoe every hand, which removes the vulnerability entirely.
Should you play it
No, for the same reason as every other side bet: without counting, Over 13 costs you 6.55% and Under costs 10.07%, against 0.46% for the hand you are already playing.
With counting it is a different question, and one we worked through separately. The short version is that the conditions that made it beatable are exactly the conditions casinos removed.
Keep reading
By Martin Kosek · every number on this site is computed by us, not copied.
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