What is overround in betting?
Overround is the amount by which the implied probabilities of all outcomes in a betting market add up to more than 100%, and it represents the bookmaker's built-in profit margin.
In a fair market, the chances of every possible outcome add up to exactly 100%. In a bookie’s market they add up to more. That surplus is the overround, and it’s how the bookie gets paid.
It’s a British term. You’ll also see “margin”, “book percentage” or “over-round”. Americans call the same thing juice, vig or “the hold”.
Example
A football match is priced Home 2.40, Draw 3.30, Away 3.00. Turn each price into an implied probability by dividing 1 by the odds:
| Outcome | Odds | Implied chance |
|---|---|---|
| Home | 2.40 | 41.7% |
| Draw | 3.30 | 30.3% |
| Away | 3.00 | 33.3% |
| Total | 105.3% |
The overround is 5.3%. One way to see what it costs you: multiply a price by the total to estimate the fair odds. Home at 2.40 × 1.053 = about 2.53. The bookie is paying 2.40 on something that, by their own numbers, deserves 2.53.
Where you’ll see it
You won’t. No bookie prints it. You have to work it out, which takes thirty seconds and is worth doing. As a rough picture:
- Main markets on big football matches and major US sports have the lowest margins.
- Exchanges are close to 100% before commission.
- Correct score, first goalscorer, outrights with many runners and bet builders carry much more.
Watch out
Overround compounds in accumulators. Put four legs together, each with a 5% margin, and you’re giving away roughly 1.05 × 1.05 × 1.05 × 1.05 = 1.22, or about 18% of the fair payout.
You can’t remove the margin. You can shrink it by comparing bookies and taking the best price on each bet. That habit alone is worth more than most tips.