Note: the article and tool below is for experienced bettors. If you’re new to sports betting and have never placed a bet, visit our page on NFL bet types.
Advanced Look at NFL Point Spreads
The half-point calculator to the left calculates the fair price for half-point buys in NFL football betting. This tool is helpful for both line shopping and purchasing half points with bookmakers. Regarding line shopping say BetOnline is offering Patriots -4 -110 and Bovada is offering Patriots -3 -140. To determine which is the better bet enter -4 and -110 into the calculator and you’ll see the -3 equivalent of -4 -110 is -3 -142.6. In this example -3 -140 at Bovada is a better bet than -4 -110 at BetOnline.
Understand our calculator uses NFL averages. In cases of games where the over/under betting line is high (say 45.5+) each half point will be worth a little less. So if our calculator tells you -4.5 -105 is the same as -4 -111.5 it might actually only be worth -111. In cases where the total is low (say 40.5 or less) each half point is worth more. In the same example -4.5 -105 might be worth -4 -112 instead of the -111.5 our calculator displays. The point is you’ll need to make small adjustments for games with a lower or higher than average over/under betting total.
Fair Odds (No-Vig): Also understand our calculator deals with fair odds. We do not attempt to determine how much vig was in the moneyline odds entered and propriate an equivalent the same way our no-vig calculator does. In short if the fair odds were -10 -110, we’ll show you the equivelent fair odds for -9.5, -9.0 and -8.5. Creating advanced NFL push charts and doing out the math can lead to much more precise results; however our calculator works extremely well on average and can be a great time saver.
Understanding Buy Point Strategy
Our NFL Half Point Calculator is a great time saver. However, when dealing with point spreads that have juice, or when you desire to be more precise, understanding the math behind half points is helpful. In this article I’ll cover this topic in some depth.
Calculating Half Point Equivalents
The first thing to understand is that all prices have an implied probability equivalent. For -3 -111 the -3 is the point spread and the -111 is the price. To calculate the implied probability we need to use the formula risk/return=implied probability. To be clear return includes both stake plus win, so for example at -111 a bet of $111 to win $100 has a return of $211 (stake+win). In this example 111/211= 0.5261 which changed to a percentage is 52.61%. This means when betting at -111 you’ll need to win 52.61% of the time to break even and this 52.61% is referred to as the implied probability.
Let’s examine -3 -111 moved to -2.5. All that’s change here is we win instead of push when the favorite wins by exactly three. To calculate the -2.5 equivalent we need to determine exactly how often teams favored by -3 win by exactly 3 points. Using a combination of historical results data and no-vig lines at sharp betting sites I determined this happens about 9.80% of the time. I just calculated one paragraph up that -111 has a 52.61% equivalent. If I add half 9.8% I get an implied probability of 57.51%. I can now go to our odds converter, plug in 57.51% in the implied probability field and see in American odds format this is -135. Therefore -3 -111 and -2.5 -135 have the same expected win/loss.
Why did I use only half of 9.8%? If we were moving from -3.5 to -2.5 I could have used the full 9.8% probability of 3 as we’d of picked up all of that probability. The reason I couldn’t do this is because we were moving from a push to a win (I also would use half when moving from a loss to a push). You see that 9.8% is built half into our line of -3 and half in the opposite team’s line of +3 and for this reason we can only take half the probability.
When should I Purchase Half Points?
The first thing to understand is not all half points are created equal. For example the push probability of 3 is about 9.8% and the push probability of 7 is about 5.72%. These are the two most common margins of victory. Meanwhile -9 only pushes 0.9% of the time, and -12 about 0.44% of the time. Many online sportsbooks sell half points involving the 7 for 15 cents, half point involving the 3 for 25 cents and all other half points at 10 cents each. Under this cost per half point pricing there are only sixteen scenarios where purchasing half points is a better bet than passing on the option to do so.
When to Purchase Two Half Points
- -3.5 purchase to -2.5 by purchasing two half points for 50 cents
- +2.5 purchase to +3.5 by purchasing two half points 50 cents
- -10.5 purchase to -9.5 by purchasing two half points 20 cents
- +9.5 purchase to +10.5 by purchasing two half points 20 cents
- -14.5 purchase to -13.5 by purchasing two half points 20 cents
- +13.5 purchase to +14.5 by purchasing two half points 20 cents
- -17.5 purchase to -16.5 by purchasing two half points 20 cents
- +16.5 purchase to +17.5 by purchasing two half points 20 cents
When to purchase One Half Point
- -3 to -2.5 by purchasing one half points for 25 cents
- +3 to +3.5 by purchasing one half points 25 cents
- -10 purchase to -9.5 by purchasing one half points 10 cents
- +10 purchase to +10.5 by purchasing one half points 10 cents
- -14 purchase to -13.5 by purchasing one half points 10 cents
- +14 purchase to +14.5 by purchasing one half points 10 cents
- -17 purchase to -16.5 by purchasing one half points 10 cents
- +17 purchase to +17.5 by purchasing one half points 10 cents
Outside of these scenarios when half points cost 25 cents involving point spreads of 3, 15 cents involving point spreads of 7 and 10 cents for all other half points, there are few other circumstances when buying half points makes sense. The one known exception is in cases of -7.5 -115 or +6.5 -115, here purchasing two half points for 15 cents each is slightly better than passing on the option. Just make sure via line shopping you can’t beat the -115 because if you can beat it betting straight would be the better play.
Half Point FAQ
Q. How do I develop a push chart?
A. Historical data weighed 25% and removing vig from Pinnacle Sports lines weighed 75% is a decent rough way to go about it. To get really advanced you’d need to simulate the actual game.
Q. What Push Probabilities Does the Half-Point Calculator Use?
A. Our tool uses the following push probabilities: -1 (2.50%),-2 (1.98%), -3 (9.80%), -4 (3.00%), -5 (1.68%), -6 (3.40%), -7 (5.72%) -8 (2.14%), -9 (0.90%), -10 (4.92%), -11 (2.22%), -12 (0.44%), -13 (1.33%), -14 (4.9%), -15 (1.46%), -16 (3.48%), -17 (4.55%), -18 (2.33%).
Q. Which Sportsbooks offer half point buys?
A. The majority of online sportsbooks offer this, the only one I’m aware that doesn’t is bovada.lv. Bookmaker.eu, BetOnline, Legends, 5Dimes etc. all offer this feature.
Editor’s note: If you enjoyed this article and are looking to learn more about football betting I suggest visiting our hub on football betting strategy.
Author & Professional: Jim Griffin