Calculate Half-Point Value
Cost and value of buying half a point on a spread.
How to Use This Calculator
- Enter the current point spread
- Enter the odds at that current spread (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 the half point pays off
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 coughing up extra juice (worse odds) to nudge the spread 0.5 points your way. Shifting from -3 to -2.5, for instance, wipes out any 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 rules the board (~15% of games), then 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 worth it at standard prices, since games land on 3 roughly 15% of the time. Buying off non-key numbers rarely justifies the added cost.
Does this hold up for the NBA?
NBA winning margins spread out far more evenly, so no single number carries the weight that 3 does in the NFL. Key NBA numbers are much softer, which makes half-point buys generally less worthwhile.