Talk to any professional bettor about the keys to their trade, and phrases like “beating the closing number” and “targeting positive EV bets” will be prominently featured in their explanation. While sharp bettors are often glorified thanks to the lofty status they occupy atop a multi-billion dollar industry, in reality their lives aren’t all glitz and glamour.
To the contrary, betting on sports for a living requires expending a lot of sweat and labor in order to gain the slightest of edges over the sportsbooks. And because sportsbooks traditionally attach a 10 percent house tax to most wagers (also known as the vigorish or “vig”), any edge has to be rooted in a base 52.38 percent success rate. That is the rate at which a bettor must win (outlined below) in order to break even against the vig.
Break-even percentage: Price / (1 + Price)
For illustration using a $1 bet and 10 percent vig:
Break-even percentage = Price / (1 + Price)
Break-even percentage = 1.10 / (1 + 1.10)
Break-even percentage = 1.10 / 2.10 = .5238
Break-even percentage = 52.38 percent
One way pros will look to gain an edge is by targeting moneylines and determining if they are correctly priced in correlation to the long-term probability of the outcome in question. Most betting sites offer conversion calculators for bettors, but the math isn’t very complicated (see below) to hand-calculate the implied probability for both minus-moneylines and plus-moneylines.
Implied probability for a minus-moneyline: (- (minus-moneyline odds) ) / ( – (minus-moneyline odds) + 100)
Implied probability for a plus-moneyline: 100 / (plus-moneyline odds + 100)
For illustration using a -150 moneyline and converting it to an implied probability:
Implied probability = (- (minus-moneyline odds) ) / ( – (minus-moneyline odds) + 100)
Implied probability = (- (-150) ) / (150 + 100)
Implied probability = 150 / 250 = .60
Implied probability = 60.0 percent
For illustration using a +150 moneyline and converting it to an implied probability:
Implied probability = 100 / (plus-moneyline odds + 100)
Implied probability = 100 / (150 + 100)
Implied probability = 100 / 250 = .40
Implied probability = 40.0 percent
Once bettors are able to determine the implied probability of a moneyline, the final step to finding a potential edge involves researching the history of that moneyline to see if it’s properly priced. Of course, for many numbers that research is not black and white, and would thus require more developed and nuanced handicapping in order to be properly executed. However, for some bets, particularly props, the information is readily searchable.
Take, for instance, the “Will there be 3 straight scores by one team?” proposition that is ubiquitous on all Super Bowl prop sheets. The pricing of that prop is always slanted toward the negative outcome, with most sportsbooks pricing the “NO” at around +150. Conversely, bettors must pay significant juice in order to bet the “YES,” with -180 representing the most common price offered.
Now at first glance, both the price attached to the “NO” (very appealing) as well as common knowledge about Super Bowls (tightly-contested affairs) would indicate “NO” is the way to go when betting that prop. However, a quick inspection of Super Bowl box scores will show that 36 of 52 Super Bowls — or 69.2 percent — have featured one team scoring three straight times. File that away for the moment. Next, calculate the implied probability of the -180 price attached to the “YES”:
Implied probability = (- (minus-moneyline odds) ) / ( – (minus-moneyline odds) + 100)
Implied probability = (- (-180) ) / (180 + 100)
Implied probability = 180 / 280 = .6428
Implied probability = 64.28 percent
When juxtaposed, it becomes clear that the implied probability of the “YES” price (64.28 percent) is markedly lower than the ACTUAL HISTORY of the “YES” outcome (69.2 percent). Which is to say that sportsbooks are ceding an edge of nearly 5 percent to anyone who bets “YES.” Furthermore, it shows that a fair-market price of the “YES” is in fact more like -220 or -225.
Again, this example is anecdotal and therefore certainly oversimplifies the process, but the applicable takeaway is that possessing even a basic understanding of how a moneyline correlates to an implied probability can go a long way toward discovering those small edges that professional bettors consistently exploit to beat the book.