Sports betting house edge: what every bet costs
A bet at −110 on a game that could go either way has a house edge of 4.55%: on average the bookmaker keeps 4.55% of everything staked. Parlays multiply it: 8.88% with two legs, 13.03% with three and 20.75% with five. Real results are in the same range. In 2025, New Jersey’s sportsbooks kept 3.8% to 5.2% of the money bet on football, basketball and baseball, and 19.2% of the money bet on parlays.
How do you find the bookmaker’s margin in a set of prices?
Turn each price into the chance it implies, which is 1 divided by its decimal odds, and add the chances up. Whatever the total has above 100% is the bookmaker’s margin. Spread evenly over the outcomes, it gives every one of them a house edge of 1 − 1/total.
| Prices | Implied chances add up to | House edge |
|---|---|---|
| −105 / −105 | 102.44% | 2.38% |
| −110 / −110 | 104.76% | 4.55% |
| −115 / −115 | 106.98% | 6.52% |
| −120 / −120 | 109.09% | 8.33% |
| −115 / −105 | 104.71% | 4.50% |
| −150 / +130 | 103.48% | 3.36% |
| −200 / +170 | 103.70% | 3.57% |
| −300 / +250 | 103.57% | 3.45% |
| +120 / +230 / +250 | 104.33% | 4.15% |
American odds become decimal odds as 1 + 100 ÷ the number for a favorite (−110 is 1.909) and 1 + the number ÷ 100 for an underdog (+130 is 2.30). Rows with three prices are markets with a draw, like a soccer result.
How much do parlays cost?
A parlay pays the product of its legs’ prices, so it multiplies their margins too. With every leg at −110, a two-leg parlay has a house edge of 8.88%, three legs 13.03% and five legs 20.75%.
| Legs | Chance to win | Pays | A fair bet would pay | House edge |
|---|---|---|---|---|
| 2 | 25% | 2.64 to 1 | 3 to 1 | 8.88% |
| 3 | 12.5% | 5.96 to 1 | 7 to 1 | 13.03% |
| 4 | 6.25% | 12.28 to 1 | 15 to 1 | 16.98% |
| 5 | 3.125% | 24.36 to 1 | 31 to 1 | 20.75% |
| 6 | 1.563% | 47.41 to 1 | 63 to 1 | 24.36% |
| 8 | 0.391% | 175.45 to 1 | 255 to 1 | 31.08% |
| 10 | 0.098% | 642.08 to 1 | 1,023 to 1 | 37.20% |
The chance to win assumes every leg could go either way. For legs at different prices, multiply what each leg returns: a leg with a 4% margin returns 0.96 of each unit staked, so three of them return 0.96 × 0.96 × 0.96 = 0.885, a house edge of 11.5%.
What do sportsbooks actually keep?
In 2025 New Jersey’s sportsbooks kept 9.5% of the $12.2 billion bet on settled events, and Nevada’s kept 7.45%. In New Jersey the gap from the 4.55% of a single bet at −110 is parlays: they were 32% of the money bet and 65% of what the books won, and on every other bet the books kept 4.9%.
| Bets on | New Jersey | Nevada |
|---|---|---|
| Football | 5.2% | 7.98% |
| Basketball | 3.8% | 5.88% |
| Baseball | 4.3% | 7.18% |
| Hockey | not listed | 8.50% |
| Other sports | 6.2% | 9.21% |
| Parlays | 19.2% | 32.59%parlay cards only |
| All sports bets | 9.5% | 7.45% |
Each figure is the regulator’s own: what the books won as a share of the money bet in 2025.
New Jersey reports parlays as a category of their own. Nevada lists only parlay cards apart, so its other parlays are inside each sport’s figure and the two columns are not like for like.
New Jersey’s figures are unaudited and may be amended.
Sources: New Jersey Division of Gaming Enforcement, December 2025 results (year to date); Nevada Gaming Control Board, Monthly Revenue Report, December 2025 (twelve months).
What does the house edge mean for a bettor?
A house edge of 4.55% means losing 4.55 for every 100 staked on average, however any one weekend goes. To come out ahead at −110 you have to win more than 52.38% of your bets.
For comparison, a bet on a single-zero roulette wheel costs 2.70% and on a double-zero wheel 5.26%. A bet at −110 sits between them, and a three-leg parlay (13.03%) costs more than either.