Overround
The amount the probabilities behind a market's odds add up to beyond 100%, which shows how big the book's margin is.
Overround (marge) sounds technical, but it's simple. Turn every price in a market into a percentage, add them up, and see how far past 100% you land. That excess is the book's margin.
Example: 60-minute line on a Habs game
A regulation-only line has three outcomes, since the game can be tied after 60 minutes. Illustrative prices:
| Outcome | Odds | Implied % |
|---|---|---|
| Habs win | 2.60 | 38.46% |
| Tie after 60 | 4.10 | 24.39% |
| Ottawa win | 2.35 | 42.55% |
| Total | 105.40% |
Overround: 5.4%. In plain words, the book pays back about 94.9% if bets come in balanced across the three outcomes.
Compare with Mise-o-jeu
When the online-only Mise-o-jeu+ launched in December 2015, Loto-Québec announced a payout rate of 90% on most bets. Flip it around: 100 / 90 = 111.1% total, an overround of about 11.1%. That's the kind of comparison overround lets you make in seconds. Prices change, so check current lines yourself.