The majority of online sportsbooks offer the ability to purchase half points off point spreads and totals. This is generally at 10 cents each. If a point spread is 5.5 you can bet the favorite -5.5 -110, -5 -120, or -4.5 -130 or the underdog +5.5 -110, +6 -120, +6.5 -130. The same can be done for over/under betting (NFL based). In this article I explain when it is and isn’t mathematically correct to purchase half points.
Half-Point Betting Math
The math to evaluate value a half point purchase is simple. For starters use an odds converter. On that page you can enter -110 and see under implied probability it shows 52.38%. This is how often a bet at -110 needs to win to average break even. If you now enter -120 you’ll see the required win percentage to break even becomes 54.55%. That’s a difference of 2.17%.
To put this into perspective let’s say we’re looking at an NBA point spread +6.5 -110. Based on the math above we would only instead bet +7 -120 if having +7 instead of +6.5 increases our expected win rate by the required 2.17%. Well, I happen to have a push chart that shows NBA teams that are favored by about 6.5 points win by exactly 7 about 4.1% of the time. In this case we are going to pass on buying the half point because we are only increasing our cover rate by 2.05% (half of the 4.1% probability of the favorite winning by exactly 7) and needed 2.17%+.
Are you confused about why we only took half the 4.1%? To explain: When we had +6.5 if the game ended with the favorite winning 7 we lost and the bookie who had -6.5 won. Moving to 7 both of us push. Therefore that extra 4.1% of value for teams winning by exactly 7, half is on our line of +7 and half is in the bookies line of -7. We gained his share of the 7 on that move. When going from a push to a win the same is true. For example: when going -7 to -6.5 or going +6.5 to +7 our push probability increases by half the probability of that game ending with the favorite winning by 7 points.
Creating Push Charts
It is important to understand each half-point has unique value. In NFL football nearly 16% of all games are decided by EXACTLY 3 points and nearly 10% by EXACTLY 7 points. Those are the two most common margins of victory. In basketball end game strategy with intentional fouls, killing clock, playing for final shots, etc. leads to certain numbers being more likely to occur than others. In low scoring sports like hockey and soccer the chances a total will be an odd (instead of even) number is significant. So the calculations will need to be ran separately for each half point.
It is a good idea to do these well in advanced. How to go about it for most sports would be using point spreads of +/- 1.5. What this means is to calculate the push rate on favorite by 6, look for all similar games where the point spread was between 4.5 and 7.5 and see how often those games finished with the favorite winning by EXACTLY 6. If you calculate this in advanced and list it in a spreadsheet or even just draw some sort of table or list it in a note pad you’ll have it handy anytime it is needed.
As far as getting the data two of my recommended books about sports betting contain value for this. Sharp Sports Betting by Stanford Wong, while outdated, has push charts inside it. These can be used as a rough guide. Or you can use SBR’s half point calculator to capture their push rates on sides and totals for NBA, College Hoops, NFL, College Football, MLB and NHL. Their data is also outdated. It is the other book Conquering Risk that has more value to serious punter. This covers how to scrape content from the web.
If you decide to scrape data there are many potential sources. One is Covers.com which has historical spreads and results going back many years. A better source for recent years is SBROdds.com. Here the calendar at the top (to the right of where it says today / yesterday) can be used to navigate through historical odds and results at multiple sportsbooks. The best one to scrape and use is Pinnacle Sports. Once you have the database – you can create your push chart.
Finding Value Buying Half Points
The key to finding value in purchasing half points is to understand the more half-points you purchase the more each is worth in value. Let me show you why. Let’s say a bookie offers up to 8 half points at 10 cents each. So this is -110 (52.38% implied probability) vs. +8 -190 (65.52% implied probability).The difference is 13.14% or in other words 1.64% per half point. That’s much better than the 2.17% paid when going from -110 to -120. How is this the case?
The reason is because moneylines are based on percentages. 10 cents means nothing in and of itself. To show this further again -110 to -120 increases the required win rate to break even by 2.17%. Again, using our odds converter I can see -120 has an implied probability of 54.55% and -130 of 56.52%. Here the move is again 10 cents but the difference is 2.03% not 2.17%. In that NBA example earlier, the 7 was worth 2.05%. Had the question been +6.5 -120 or +7 -130 we would take +7 -130 because the push on 7 increases our win rate by more than the 2.03% difference in implied probability.
To give an extreme example, going from -180 (64.28%) to -190 (65.52%) has a difference of just 1.24%!. The bigger the moneyline odds the more likely it is that purchasing a half point at 10 cents is a good deal! So how can we can we make money from this?
As a general rule of thumb in basketball it takes 6 half points at 10 cents each to have a tiny edge over the bookmaker. If you can do more than that, with good bankroll management, you practically have a money printing machine. For example 4 points for -190 instead of -110 gives an expected ROI of about 3.6%. While sites like BetUs.com (not very reputable) used to offer 8 points for 80 cents, today most bookies are wise and such deals are uncommon. The smartest bookies limit the number of half points that can be purchased to 2 or 3 before they start to charge a premium.
The most logical place to find value should be in NFL point spreads on the most common margins of victory 3 and 7. Unfortunately, here once again the bookies charge a premium. Going from +2.5 to +3, +3 to +3.5, -3.5 to -3, and -3 to -2.5 costs 25 or 30 cents at most bookies. Going from +6.5 to +7, +7 to +7.5, -7.5 to -7, and -7 to -6.5 costs 15 or 20 cents. This can still sometimes be worth it when the ML is large. What is however more common is to find value on the half points they don’t charge a premium for. Worth noting is that the third most common margin of victory in NFL football is 10. Should I continue?
Let me just tell you buying half points is one of the many ways I personally make money betting sports. If I however told you which sites allow 4 half points at 10 cents each (yes these exist) or what the most common margins of victory are for every league, this article will become outdated quickly. Why? Because everyone will be beating the sportsbook that offers +EV point buy opportunities. That book will eventually notice and adjust their odds. This has happened many times in the past. Years ago basic strategy NFL teasers were profitable at most sites, today they are not. Years ago there was much more value in buying half points, but today bookies grown wiser.
If you do the work to make push charts, find the most common margins of victory, and learn which bookies offers what, you will soon be able to create a system. Every time a specific point spread pops up you know “at book XYZ I need to do X”. If you have that system you are making money. At that point you will be glad I concluded this article the way I did. It is important only a limited number of people take advantage of the +EV angles, because eventually they dry up.
Author: Jim Griffin