Should You Buy a Half-Point in Super Bowl 51?

When the Super Bowl 51 line was released last Sunday, the New England Patriots opened as 3-point favorites against the Atlanta Falcons across the sports betting marketplace. Despite one-sided public betting on the chalk, every single offshore sportsbook is still hanging New England -3. That raises an interesting conundrum for bettors who want to place a wager on the spread: Should I take the current price, or buy a half-point?

Most bettors are already familiar with the concept of key numbers but, for any novice bettors, these are the most common margins of victory in the NFL. Since field goals are worth three points and touchdowns (assuming a successful PAT) are worth seven points, most games are decided by some combination of these numbers.

Using our historical database, I found that “3” has been far and away the most significant number for bettors. Since the start of the 2003 season, roughly 15% of all games have been decided by exactly three points, and this is crucial for spread bettors. We always advocate that bettors have access to multiple sportsbooks and shop for the best line, but that philosophy is exemplified when we’re dealing with a key number.

Since 2003, there have been 615 games in which one team closed as a 3-point favorite at Pinnacle, which makes it the most common closing spread in our database. In that sample, the favorite has won by exactly 3-points on 53 occasions. That means there’s an 8.62% probability that Super Bowl 51 bettors taking spread would have their wager result in a push.

Most sportsbooks allow football bettors to buy points on spread; however, there’s normally a premium for when you’re buying off a key number. Generally speaking, it costs about 25 cents for to buy off the 3, 15 cents to buy off the 7, and 10 cents for all other half-points. That means bettors who would otherwise take New England -3 (-105) would instead take New England -2.5 (-130). Similarly, bettors who would otherwise take Atlanta +3 (-115) would instead take Atlanta +3.5 (-140).

Assuming the standard -110 juice, spread bettors would need to win 52.38% of their wagers to break even. That said, the current spread juice slightly favors the Falcons as Atlanta (-115) would need to cover the spread 53.49% of the time and New England (-105) would need to cover the spread 51.22% of the time to break even. After buying the half-point off 3, Atlanta (-140) would need to cover the spread 58.33% of the time and New England (-130) would need to cover the spread 56.52% of the time to break even.

Our previous analysis found that it would be unwise to buy a half-point from +2.5 to +3 and that it’s actually preferable to take small underdogs on the moneyline as opposed to the spread. I have already shown that 3-point favorites/underdogs will push in 8.6% of their games, and buying the half-point will turn all of those pushes into wins. However, the increased juice causes the average units won to decrease considerably. A $100 wager at -110 odds would yield a $90.91 profit, but a $100 wager at -135 odds would only yield a $74.07 profit.

If you already liked Patriots -3 (-105), then it would be a poor decision to buy the half-point and take Patriots -2.5 (-130) since it increases the bookmaker’s advantage. Likewise for bettors who intend on buying the Falcons from +3 (-115) to +3.5 (-140). For more evidence that it’s inadvisable to buy the half-point, we’ll test the hypothetical return on investment for both examples.

Based on our earlier findings and the current spread juice, the current implied odds are suggesting Atlanta will cover 46.85% of the time, New England will cover 44.53% of the time, and the game will push 8.62% of the time.  Using that as our starting point, let’s examine the hypothetical situation where we take Atlanta +3 (-115) and Atlanta +3.5 (-140).

  • Falcons +3 (-115): 46.85 – (1.15 x 44.53) = -4.36%
  • Falcons +3.5 (-140): 55.47 – (1.4 x 44.53) = -6.87%

When you buy the half point, the return on investment actually drops by 2.51 percent, which indicates it’s an unwise decision. That math assumes a 50% win rate for both teams, but historically small underdogs have provided solid value. Since 2003, 3-point underdogs have gone 298-264-53 against the spread (+22.18 units) and 265-349 straight up (+33.31 units). The table below displays the historical value of 3-point favorites and 3-point underdogs.

Should you buy the half-point on 3-point favorites?

Bet Type Record Win Rate Units Won/Lost ROI
-3 (Spread) 264-298-53 ATS 47.0% -45.48 -8.1%
-3 (Moneyline) 349-265 SU 56.8% -41.76 -6.8%
Bought to -2.5 (Spread w/ 25 cent juice) 317-298 ATS 51.5% -54.78 -8.9%

Should you buy the half-point on 3-point underdogs?

Bet Type Record Win Rate Units Won/Lost ROI
+3 (Spread) 298-264-53 ATS 53.0% +22.18 +3.9%
+3 (Moneyline) 265-349 SU 43.2% +33.31 +5.4%
Bought to +3.5 (Spread w/ 25 cent juice) 351-264 ATS 57.1% +8.84 +1.4%

Although the winning percentage increases substantially when bettors buy a half-point off 3, the increased juice means fewer units won on those wagers. Even though 3 is the most common margin of victory in NFL games, it’s not worth paying a premium to get the hook. In fact, Falcons bettors may want to consider taking the moneyline as opposed to the spread.

It’s difficult to definitively prove that bettors shouldn’t buy the half-point in this situation, especially given the recent changes to the extra point and the increased propensity for teams to attempt the two-point conversion. That said, recent history indicates bettors should only buy that half-point if it costs 20 cents or less.

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David Solar

David Solar is the Content Manager at Sports Insights. He specializes in sports betting analytics and creating data-driven betting systems. He can be reached directly at david@sportsinsights.com or on twitter at @TheDavidSolar.

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