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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Convert American NFL betting odds into a break-even probability with a simple formula: for positive odds, divide 100 by the odds number plus 100; for negative odds, divide the absolute odds by that number plus 100. At -110, for example, the break-even rate is 52.38%. That is the rate needed to break even at the quoted price over repeated bets—not a prediction that the bet has a 52.38% chance to win.
Use the formula for American odds
The result is a percentage. For negative odds, use the odds’ absolute value in the calculation.
- Positive odds (+X): Implied probability = 100 ÷ (X + 100) × 100.
- Negative odds (-X): Implied probability = X ÷ (X + 100) × 100.
These formulas convert the price into its break-even rate before accounting for the bookmaker’s margin. DraftKings’ odds guide illustrates the same calculation with +120, which converts to 45.45%, and -120, which converts to 54.55%.
Examples
| American odds | Calculation | Break-even probability |
|---|---|---|
| +150 | 100 ÷ (150 + 100) × 100 | 40% |
| -150 | 150 ÷ (150 + 100) × 100 | 60% |
| -110 | 110 ÷ (110 + 100) × 100 | 52.38% |
What -110 means
At -110, a winning bet risks $110 to earn $100 in profit; the original stake is returned as well. Over repeated bets made at that same price, you need to win 110 out of every 210 bets—about 52.38%—to break even, assuming the bets settle as wins or losses without pushes or other refund conditions.
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The percentage describes the price’s break-even threshold. It does not mean the sportsbook has established that the team, spread bet, or total has exactly that chance of winning.
Why two -110 sides add up to more than 100%
For a two-outcome spread or total with both sides priced at -110, each side’s raw implied probability is 52.38%. Add them and the total is about 104.76%. The portion above 100% is the overround, commonly called the vig or juice in US betting. Because the raw percentages include the margin in the prices, they are not mutually compatible estimates of the event’s real probabilities.
Overround is useful for comparing prices, but it is not automatically the exact loss rate bettors will realize. A University College Dublin School of Economics working paper discusses how the familiar calculation depends on assumptions about how margins are distributed across outcomes; it also considers favorite-longshot bias. Its empirical examples concern soccer and tennis, not NFL betting, so they should not be read as NFL-specific findings. See the paper’s discussion of overround and bookmaker margins.
Calculate a simple no-vig estimate
To remove the overround using proportional normalization, calculate the raw implied probability for each mutually exclusive outcome, add those probabilities, then divide each side’s raw probability by that sum. A University of Reading economics working paper describes this method; the paper’s repository filename indicates approximately 2020, and it was accessed October 4, 2026. Read the paper’s explanation of implied probability and normalization.
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- Convert each side’s odds to a raw implied probability.
- Add the raw probabilities for all outcomes in the market.
- Divide each side’s raw probability by the combined total.
For -110/-110, the raw rates are about 52.38% each and total 104.76%. Dividing each by 104.76% gives 50% per side. These are normalized, no-vig estimates—not definitive or objective probabilities. Proportional normalization assumes the margin is distributed proportionally between the outcomes.
Apply the conversion to NFL markets
Moneyline
Use the listed American odds for the team. The conversion gives that price’s break-even rate for a bet on the team to win.
Point spread
Use the odds attached to the exact spread wager. The result is the break-even rate for that bet at that spread and price; the formula does not calculate the chance of covering a different spread.
Game total
Use the odds attached to Over or Under at the listed total. The result is the break-even rate for that side at that price, not a forecast generated from team statistics.
Best Value
If a market includes pushes, alternate lines, or a refund condition, its settlement rules matter. The simple conversion does not account for those conditions unless the quoted odds and settlement format explicitly support that treatment.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Compare prices without comparing different bets
When comparing sportsbooks’ prices, compare the same market, exact line, and settlement rules, with odds captured at the same time. Convert both sides at each book, then compare each side’s raw implied probability and the combined overround. A percentage from one spread or total line is not directly comparable to a percentage from a different line: they describe different wagers. Overround can help show which matched market has the lower combined margin, but it does not guarantee a particular realized loss rate.
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