Download the appBy Outlier · Updated
About the Half Point Calculator
A half point matters when the final score lands on the whole number next to it. This tool uses your estimates for those results to compare fair odds on nearby spreads or totals.
How to use this calculator
- Choose a team spread, over, or under. Enter the starting line and both sides’ odds.
- For a whole-number line, enter the chance of a push at that number.
- For a half-point line, enter the chance of landing on each nearby whole number.
- Compare the lower, starting, and higher lines. Check both the win and push chances.
Formula and definitions
- Remove the baseline margin: p = (1 ÷ d₁) ÷ [(1 ÷ d₁) + (1 ÷ d₂)].
- At a whole-number baseline: win chance = p × (1 − q).
- Moving half a point shifts the chance at the affected number between a win, push, and loss.
- Fair decimal odds = (1 − push chance) ÷ win chance.
- Baseline
- The starting spread or total.
- d₁ and d₂
- Decimal odds for the selected side and the opposite side.
- p
- The adjusted win chance among results that do not push.
- q
- The chance of a push, written as a decimal. An 8% chance is 0.08.
- Boundary probability
- Your estimate of how often the result lands on an affected whole number.
Worked example
- Start at -3 with -110 on both sides and an 8% chance of winning by exactly 3.
- At -3, the model gives a 46% win chance, 46% loss chance, and 8% push chance.
- At -2.5, the push becomes a win: 54% win chance and about -117 fair odds.
- At -3.5, the push becomes a loss: 46% win chance and about +117 fair odds.
How to read your result
A higher line helps a selected team’s spread or an under bet. A lower line helps an over bet.
When a result can push, the fair odds account for the chance of getting your stake back.
Assumptions and limitations
- You supply the chances at the affected whole numbers. The defaults are examples, not measured rates from league results.
- Both starting prices must cover opposite sides of the same market with matching push and settlement rules.
- Only whole-point and half-point lines are supported. Fair odds use proportional margin removal and may differ from a sportsbook’s offered odds.
Common mistake to avoid
Half points are not all worth the same amount. Turning a loss into a push differs from turning a push into a win.
Put your result to work
Try a related calculator, or read our sports betting strategy guides to learn more.
- Point Spread Calculator — Spread to moneyline
- No-Vig Fair Odds Calculator — Odds without sportsbook margin
- Expected Value Calculator — Average profit or loss
Half Point FAQs
Is buying half a point worth it?
It depends on how often the result lands on that number and the extra cost. Compare the fair odds from your assumptions with the sportsbook’s price for the new line.
Where do boundary probabilities come from?
Use relevant past results or a scoring model to estimate how often each whole number occurs. You supply those estimates here. The starting values are examples.
How results are calculated
Results use the formulas and assumptions above. Money is rounded to cents. Odds and percentages are rounded to make them easier to read.
The starting values are examples. Enter your own estimates. This tool does not load historical results.