Prop Betting in Sports

A Prop bet, also referred to as proposition bet, is a wager on any special set of circumstances outside the betting norm. A few crazy prop bets publicized on internet gambling forums in recent years included whether a gambler could eat 450 hotdogs during the month of April (15 per day), whether or not Huck Seed could stand shoulder deep in the ocean for 18 hours, and whether someone could turn $10 into $10K in 14 days playing sit and go poker tournaments.

While all these are great examples of entertaining prop bets, in sports betting there are less exciting, yet often times profitable prop bets available. We’ll cover that topic in this article.

Calculating Prop Bet Probabilities (in-depth)

In sports betting, you’ll find all sorts of prop bets, such as will there be a score in the first 7:30 of an NFL football game, will a certain team attempt over or under 13 three pointers in a game, how many points will Kobe Bryant score, and a plethora of others. The gambling site offering the largest number of propositions is, while Bodog is known for high value (+EV) props and BetUs for most outrageous and wild prop betting offers.

To give some insight into prop betting strategy, at the time of this article Pinnacle Sports is offering the following prop bet on Sunday night’s NFL football game between the Cowboys vs Packers:

The Prop Bet: Team to score first points of game?

Cowboys +140
Packers -165

We chose this example, because this is a common prop bet many sites offer. The first thing we’ll do here is go shopping for other sites offering the same prop. Here is what we find:

  • Cowboys +150 / Packers -170
  • Bodog: No Line Yet
  • Sportsbook: Cowboys +135 / Packers -165
  • Bookmaker: No Line
  • TheSportsbook: Cowboys +120 / Packers -165 (Holy Juice!)
  • TheGreek: +135 / Packers -165

I’m not going to keep digging at this point. That -165 favorite price seems to be a reoccurring theme, except for at one single site (5Dimes) that happens to have the lowest juice and the worst line on the favorite. Potentially, this could very well be a +EV bet on the underdog.

My next step here is to determine the no vig line of the two sites offering the same line ( and TheGreek), as they appear to be similar to what the other lines are based off.

If you’re not familiar with this: what we do first is come up with a break even percentage for each bet. The formula for this is risk/return=break even percentage. Let’s start with the Greek. $135 on the Packers is risk $100 to win $135, so a winning bet returns $235 (return is risk + win). The math for finding the break even percentage is 100/235= 0.425531914893617, which s 42.55%. The same math for Packers is $165 to win $100, so 165/265=0.6226415094339623 which is 62.26%.

Now let’s add the two break even numbers together and see 42.55%+62.26%=104.81%. The total is higher than 100% because juice is still included. To remove the juice, we take each break even percentage divided by the total break even percentage. 42.55%/104.81%=40.60% and 62.26%/104.81%=59.40%. We can verify the juice has been removed as the two probabilities now equal 100%.

To save the math, you can either Google search “Moneyline Converter” or refer to our article on future betting where we show converting a win probability to a moneyline. Simplifying things, we’ll just tell you Cowboys 40.60% / Packers 59.4% converted to American odds format is Cowboys +146 / Packers -146. This is what’s called the no-vig moneyline.

If we’re just betting for entertainment purposes, we might decide now, this in appearance could very well be a +EV bet. We found an underdog price at 5Dimes that is far better than what we can get anywhere else, and it beats the no-vig line at other sites. At the worst, we have a very slight disadvantage, but much less of one than any other random bet on the board, and we might actually have an advantage. Let’s go for it.

However, as a long time bettor who wants to be sure, I’m familiar with this prop and have some handicapping knowledge about how this line is set.

The best way to get rough numbers on which team will come first is to handicap based on the first half line.

Comparing a few sites I find:


Cowboys +4.5  -113 | OVER 23  -105
Packers -4.5  +102 | UNDER 23  -105

+4  -105 | OVER 23  -110
-4  -115 | UNDER 23  -110

+4  -105 | OVER 23  -110
-4  -115 | UNDER 23  -110

This pattern repeats, finding several other sites offering the same as Bookmaker and 5Dimes.

Using the spread of 4 and the total of 23, I determine the first half predicted scores to be in a range of 13-9 or 14-10. For handicapping purposes, I am going to get a little more exact.

Calculating no juice probabilities on the lines offered, I get +4 +104.43 / -4 -104.43 and +4.5 -107 / -4.5 +107. I need to get to an even line, and I’m going to make an estimate that the true point spread better convert to +4.35 +100 / -4.35 +100. The total was exactly even at every site at over under 23 (-105 / +105 and -110 / +110), so 23 is the predicted total. What I do now is take the total of 23 points, subtract the 4.35 spread and get 18.65. I divide this by two, and give each team 9.33 points each, and add back the 4.33 to the favorite. I now have a predicted first half score of Packers 13.68 Cowboys 9.33.

Now that we have the predicted score, we can get a good idea of the moneyline for the favorite scoring first by taking -100 * (Favorite Score / Underdog Score). Which in this case is -100*(13.68/9.33) which equals -146. This is a no juice model, so likewise the underdog is +146. We’ve used a basic model to cap who will score first as Packers -146 / Cowboys +146.

This is the second method we’ve used which hints that the Cowboys +150 at 5Dimes is a +EV bet. If we really wanted to get more precise, we’d go find as many similar math ups as we could in historical archives to see how often the underdog scored first. That’s a time consuming process, and it is probably not worth the effort for a small market prop. At this point, being in the mood to gamble and believing this is +EV, I make the bet at 5Dimes, Cowboys to score first +150.

Prop Betting as a Pro

Prop bets are made available largely as a source for attracting and retaining recreational players. If you dominate the prop market, don’t be surprised if your max bet on props is quickly cut to $50, or you’re asked to leave certain sites. Of course, if you’re reading this article, you might be a while away from that being a consideration, but we wanted to warn you about that upfront.

As far as additional advice about prop betting, the method we covered here with line shopping, backing out juice, etc, is a great way to approach prop betting no matter what the topic. In props where there are multiple options, there are some tips that will be relevant in our article on future betting. Here, we show how to back juice out a multi way wager and calculate the betting site’s house advantage. Beyond that, there are many other tricks we’ll save for a future article, because as of right now we can’t spoon feed too much (smile) we want to continue making money betting props ourselves.

As a final note, if you’re curious about the prop bets in the intro, 450 hot dogs were eaten, Huck Seed lasted only 3 hours in the water, and, amazingly, $10 was turned into $10K over 14 days playing sit and goes. If you get good at prop betting, not only can you make a lot of money sports betting, but you can have an entertaining time gambling with friends as well.