Half Point Calc
What buying half a point costs — and if it's worth it.
How to Use This Calculator
- Enter the current point spread
- Enter the odds at the current spread, in American format (e.g., -110)
- Enter the odds if you buy a half point (e.g., -120)
- See the cost in implied probability and whether buying that half point is worth it
Formula
Implied Probability from American Odds:
- Negative: |Odds| / (|Odds| + 100) x 100
- Positive: 100 / (Odds + 100) x 100
Cost of Half Point = Implied Prob (Half Point Odds) - Implied Prob (Current Odds)
Worth buying if Cost < Probability of game landing on the number
Frequently Asked Questions
What does buying a half point mean?
Buying a half point means paying extra juice — worse odds — to nudge the spread 0.5 points your way. Shifting from -3 to -2.5, for instance, wipes out the chance of a push on exactly 3 points.
What are key numbers in NFL betting?
Key numbers are the margins games land on most often. In the NFL, 3 reigns supreme (~15% of games), trailed by 7 (~10%), 1 (~6%), and 10 (~5%). Moving off these numbers usually carries the most value.
Is buying a half point usually worth it?
Depends on the number. Buying off 3 is almost always a smart play at standard prices, since games land on 3 roughly 15% of the time. Buying off non-key numbers rarely justifies the added cost.
Does any of this apply to the NBA?
NBA margins of victory spread out far more evenly, so no single number carries the weight that 3 does in the NFL. Key NBA numbers are muted, which makes half-point buys generally less valuable.