What is a bookmaker's margin (overround or vig)?
By ProbaPredict Data Desk · Last reviewed
A bookmaker's margin is the amount by which the implied probabilities of every outcome in a market add up to more than 100%. If home, draw and away imply 105% in total, the margin (overround or vig) is 5%. It is how bookmakers build profit into prices, and it makes every bet slightly worse than fair.
How does a bookmaker's margin work?
Imagine a coin toss priced fairly at 2.00 for heads and 2.00 for tails. Each implies 50%, totalling 100%. A bookmaker might instead price both at 1.91. Each now implies 52.4%, totalling 104.8%. Whatever happens, the bookmaker expects to keep about 4.6% of all the money staked. That built-in edge is the margin.
How do you calculate the margin?
Margin = (1 ÷ odds1 + 1 ÷ odds2 + … ) − 1. For a football 1X2 market at 2.20, 3.30 and 3.40: 0.455 + 0.303 + 0.294 = 1.052, so the margin is 5.2%. The implied probability calculator works this out for any market of 2–10 outcomes.
How big are margins in football?
The table below shows the average margin built into market-average closing odds in each league we cover, measured across 17,375 matches. Across them the 1X2 average is 5.3%. Margins tend to be lower in the most heavily bet leagues and on main markets, and higher on niche markets such as correct score.
| League | Matches | 1X2 margin | Over/Under 2.5 margin |
|---|---|---|---|
| Premier League | 1,950 | 4.4% | 4.9% |
| Bundesliga | 1,566 | 4.8% | 5.2% |
| La Liga | 1,969 | 4.8% | 5.2% |
| Serie A | 1,950 | 4.9% | 5.2% |
| Ligue 1 | 1,723 | 5.0% | 5.3% |
| Championship | 2,855 | 5.5% | 5.6% |
| Eredivisie | 1,593 | 5.7% | 6.1% |
| Primeira Liga | 1,592 | 6.2% | 6.0% |
| Brasileirão Série A | 2,177 | 6.3% | not in source |
Source: ProbaPredict analysis of 17,375 matches, updated Fri, 2 Oct 2026. Market-average closing odds from football-data.co.uk. Margin = sum of implied probabilities − 100%.
Overround vs margin: is there a difference?
People use the words interchangeably, but strictly the overround is the excess over 100% (5.2% above), while the bookmaker's expected profit share is overround ÷ total book (5.2 ÷ 105.2 = 4.9%). The difference is small; both describe how much worse than fair the prices are.
Why does the margin matter to you?
Because it is a cost on every bet. If a market has a 5% margin, a bettor picking at random can expect to lose about 5% of stakes over time. Accumulators compound it: a four-fold where each leg carries a 5% margin has roughly 1.054 − 1 = 21.6% overround. See what an accumulator is.
Worked example: removing the margin
Odds: home 2.20 (45.5%), draw 3.30 (30.3%), away 3.40 (29.4%). Total 105.2%. Using the proportional method, divide each by 1.052: home 43.2%, draw 28.8%, away 28.0%. Fair odds: 2.31, 3.47, 3.57. Those are what the prices would be with no margin. Our own fair odds are calculated the same way from our model's probabilities, which have no margin to begin with (see fair odds).
How do we use margin-free closing odds?
We compare our model with margin-free closing odds in public. Closing odds are the final prices before kick-off and are among the most accurate forecasts available. On our accuracy page and in our back-test, closing odds are slightly more accurate than our model, and we publish that comparison.
UK and US terminology
UK: "margin" or "overround". US: "vig", "vigorish" or "juice". A "reduced juice" sportsbook simply has a lower margin.
Common mistakes with margins
- Ignoring it. A 5% margin is a 5% headwind on every bet.
- Assuming it's spread evenly. Bookmakers often put more margin on outsiders (the favourite-longshot bias).
- Forgetting accumulators multiply it. Each leg adds more.
- Comparing odds without removing it. Different bookmakers use different margins.
Can you reduce the margin you pay?
You can't remove it, but you can be aware of it. Comparing prices across bookmakers, sticking to main markets where margins are lowest, and avoiding stacking many legs into one bet all reduce how much margin you pay overall. None of that turns betting into a way to make money: even at low margins, the expected return of a typical bet is below what you stake. It simply means you lose less to the price itself, which is worth knowing whatever your budget.
How does margin differ by market?
Main markets such as the match result and Over/Under 2.5 attract the most money and the sharpest prices, so they usually carry the lowest margins. Niche markets such as correct score, first goalscorer or exotic combinations often carry much higher margins, sometimes 15–30%. Bet builders and same-game combinations add their own margin on top of each component.
The table above covers 1X2 and Over/Under 2.5 in market-average closing odds, which is close to the best case. Individual bookmakers' prices earlier in the week can carry more. Checking the margin with our implied probability calculator before comparing prices is a simple habit that makes comparisons fairer.
Frequently asked questions
- What is overround in betting?
- Overround is the total of a market's implied probabilities minus 100%. A book adding up to 106% has an overround of 6%.
- What is vig?
- Vig (short for vigorish) is the US term for the bookmaker's margin. A soccer total priced at -110 on both sides has about 4.8% vig.
- How do I calculate a bookmaker's margin?
- Convert each price to implied probability (1 ÷ decimal odds), add them up and subtract 100%.
- Which football league has the lowest bookmaker margin?
- In our closing-odds data, the biggest European leagues usually carry the lowest margins. The table on this page shows the current figures.
Related pages
- Implied probability and margin calculator
- How to calculate implied probability
- Fair odds explained
- Our model vs bookmaker closing odds
- How Do Betting Odds Work? Decimal, Fractional and American
- American Odds Explained: What +150 and -200 Mean
- Fractional Odds Explained: What 5/2 and 10/11 Mean
- How to Calculate Implied Probability From Odds
- All football betting guides
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