King Yao is the author of Weighing the Odds in Hold‘em Poker, and Weighing the Odds in Sports Betting. He uses his experience from making millions in financial derivative markets and translates it into gambling. Since he left his trading position in 2000, he has been playing poker and betting on sports. He travels to Las Vegas frequently, especially during football season.

Whether you are betting sports in brick-and-mortar casinos, online or anywhere else, you should have a working knowledge of the information below.


A scalp is a combination of two bets that are mirror images of each other. The combination of the two bets in a perfect scalp has zero risk and you win the same amount no matter the outcome of the event. Scalps might consist of bets that are other than perfect mirror images of each other; they may slightly favor one side over the other.

Perfect scalp

Here is an example of a perfect scalp with no risk remaining.

The Lakers are playing the Spurs.

Bet 1: Lakers +3.5 +100, risking $100 to win $100

Bet 2: Spurs -3.5 +110, risking $95.24 to win $104.76

If the Lakers cover the +3.5 point spread, your result will be:

Lakers +3.5 +100 Win +$100

Spurs -3.5 +110 Lose -$95.24

Total Result: +$4.76

If the Spurs cover the -3.5 point spread, your result will be:

Lakers +3.5 +100 Lose -$100

Spurs -3.5 +110 Win +$104.76

Total Result: +$4.76

No matter who covers the spread, the Lakers or the Spurs, your total result is the same, a profit of $4.76 on the two bets combined. This is a perfect scalp; there is no risk remaining, and you are indifferent on who covers the spread.

Imperfect scalp

Here is an example of an imperfect scalp with minimal risk remaining. The Suns are playing the Heat.

Bet 1: Suns -4.5 +100, risking $100 to win $100

Bet 2: Heat +4.5 +110, risking $100 to win $110

This is a more practical scalp because betting $100 at the sportsbook is more natural and less cumbersome than betting $95.24.

If the Suns cover the -4.5 point spread, your result will be:

Suns -4.5 +100 Win +$100

Heat +4.5 +110 Lose -$100

Total Result: $0

If the Heat covers the +4.5 point spread, your result will be:

Suns -4.5 +100 Lose -$100

Heat +4.5 +100 Win +$110

Total Result: +$10

There is a little bit of risk remaining in the scalp; you are slightly better off if the Heat cover the spread. But even if the Suns cover the spread, you do not lose anything. This is a scalp, just not a perfect one.

Negative scalp

A negative scalp is a scalp that is guaranteed to lose. Generally sports bettors are not interested in negative scalps, but they can happen sometimes. Here is an example of an intentional negative scalp:

Baylor is playing Texas Tech in college basketball. You handicap the game with Baylor -3 as the correct line. The game opens with Baylor pick ’em at -110 and you decide to make a wager.

Later in the day, before the game starts, you hear news that two star players for Baylor were just suspended for the game by the coach for curfew infractions. You know this is a big impact and without these two star players, you think the line really should be Texas Tech -1.5. You quickly check a sportsbook and discover that the line has not moved. They still have the game at pick ’em, but you have to lay -110 to bet either Baylor or Texas Tech. You decide to bet Texas Tech -110, which has a slight positive EV if the true line is Texas Tech -1.5. Normally you would not make that bet because the line is too close to your handicapping expectations and there is not enough room for error. In this case though, given you have new information and you already have a bet on the “wrong” team, a bet on Texas Tech makes sense because it has positive EV and reduces your risk.

The two bets combined is a negative scalp. No matter who wins, you will lose 10 cents due to the vig. But you do think locking into the negative 10 cents is a better alternative to letting the original wager ride. The negative scalp was intentional, and it will decrease your expected loss, and that is a good thing.

This is part of an occasional series of articles.

Excerpted with permission from the e-book version of Weighing the Odds in Sports Betting by King Yao, edited for this format.


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