Half point calculator
What a half point is actually worth — priced from 6,223 real NFL games.
Books sell half points at a flat rate. Football does not produce margins at a flat rate. Crossing 3 is worth roughly ten times crossing 9, and knowing which is which is the difference between buying a real edge and funding one.
Worth
20¢
Fair win probability
+4.57 pts
Games landing on 3
9.09%
Fair price moves
+101 → -119
| Line | Win | Push | Loss | Fair price |
|---|---|---|---|---|
| −3 | 45.19% | 9.09% | 45.72% | +101 |
| −2.5 | 54.28% | 0.00% | 45.72% | -119 |
Priced from a margin distribution fitted to 6,223 NFL regular-season games (2002–2025), residual sd 13.20 points. It answers what the half point is worth against a fair line; it does not forecast the game, and the market’s number is taken as the best available estimate.
What every half point is worth
| Buying off | Games landing there | Worth | Relative |
|---|---|---|---|
| 1 → 0.5 | 2.45% | 5¢ | 25% of the largest |
| 2 → 1.5 | 2.48% | 5¢ | 25% of the largest |
| 3 → 2.5 | 9.09% | 20¢ | 100% of the largest |
| 4 → 3.5 | 2.67% | 6¢ | 30% of the largest |
| 5 → 4.5 | 2.18% | 5¢ | 25% of the largest |
| 6 → 5.5 | 3.85% | 8¢ | 40% of the largest |
| 7 → 6.5 | 5.83% | 14¢ | 70% of the largest |
| 8 → 7.5 | 2.75% | 7¢ | 35% of the largest |
| 9 → 8.5 | 1.18% | 2¢ | 10% of the largest |
| 10 → 9.5 | 4.54% | 11¢ | 55% of the largest |
| 11 → 10.5 | 1.73% | 4¢ | 20% of the largest |
| 12 → 11.5 | 1.61% | 3¢ | 15% of the largest |
| 13 → 12.5 | 2.37% | 5¢ | 25% of the largest |
| 14 → 13.5 | 4.50% | 10¢ | 50% of the largest |
Why 3 dominates
A field goal is three points, so games end on a three-point margin more often than on any other number — about one in seven across the sample. Laying 3 pushes on those games; laying 2.5 wins them. The half point buys that band and nothing else, which is why its value is simply how often the number comes up.
The standard price for buying off 3 is 25 cents. This model says it is worth about 20. That gap is not an accident, and it is the same reason the dead numbers — 9, 11, 12 — are sold at the same flat rate as the live ones.
Where the numbers come from
A margin distribution fitted to 6,223 NFL regular-season games, 2002–2025, with a residual standard deviation of 13.20 points and a mean residual of +0.049 — meaning the market is unbiased and this model is not trying to beat it. It is derived from a joint score distribution rather than a curve drawn over margins, because margin and total always share parity and a model that gets parity wrong misprices exactly the half points it is meant to value.
Related: the Guardian Line · teaser calculator · middling calculator · line shopping guide
Common questions
- What is buying half a point worth in the NFL?
- It depends entirely on which number you cross, and the spread is wide. Buying off 3 is worth about 20 cents because roughly 9% of games land exactly on 3. Buying off 9 is worth about 2 cents. A book charging one flat price for every half point is overcharging on the dead numbers and undercharging on the ones that matter.
- Why is 3 the most important number in football?
- Because a field goal is three points and games are decided by one more often than by any other margin. In 6,223 regular-season games from 2002 to 2025, about one in seven ended on a field-goal margin. Nothing else on the board comes close, which is why the half point across 3 costs roughly ten times the half point across 9.
- Is buying half a point off 3 for 25 cents a good deal?
- On this model, no — it is worth about 20 cents, so 25 is an overpay. That is the standard price most books charge, and it is standard because it is profitable for them. The half point is still the single most valuable one available; you are just paying a premium to get it.
- How is the value of a half point calculated?
- It is the probability mass sitting exactly on the number you cross. Laying 3 pushes when the favourite wins by exactly 3; laying 2.5 wins those games outright. So the half point buys precisely that margin's frequency — nothing more — and converting that probability gain into a price gives the value in cents.
- Which key numbers matter most in NFL spreads?
- 3 first by a wide margin, then 7, then 10, 14 and 6. The dead numbers are 9, 11 and 12, where a half point buys almost nothing. The order comes from how football scoring is quantised — field goals and touchdowns — not from anything about the teams.
- Does this work for totals as well as spreads?
- The same principle applies but the numbers differ: totals cluster on different values than margins do, and this model is fitted to margins. Treat it as a spread tool. The general lesson carries over — the value of a half point is the frequency of the number it crosses, never a flat rate.
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