Every bookmaker builds a profit margin into their odds — sometimes called the "overround" or "vigorish." Here's exactly how it works and how to spot it.
If a market had no margin, the implied probabilities of all possible outcomes would sum to exactly 100%. In reality, bookmakers price markets so the probabilities sum to more than 100% — and that excess is their built-in edge, paid for collectively by all bettors regardless of who wins.
Take a simple coin-flip event with two equally likely outcomes. A "fair" market would price both at decimal 2.00 (50% + 50% = 100%). A real sportsbook might instead price it at:
That extra 4.8% is the margin. No matter which outcome occurs, the bookmaker has structurally priced themselves a small edge.
For a three-way football market (Home/Draw/Away) priced at 1.85 / 3.40 / 4.20:
| Market Type | Typical Margin |
|---|---|
| Top league 1X2 (Pinnacle-tier) | 2–3% |
| Top league 1X2 (mainstream books) | 5–8% |
| Player props / niche markets | 8–15% |
| Outright / futures markets | 15–30%+ |
Mainstream, high-volume markets on sharp bookmakers (like Pinnacle) carry the lowest margins because competition and bet volume force prices toward efficiency. Niche markets and long-term outrights carry much higher margins since there's less competitive pressure and more pricing uncertainty for the book.
For the next step, read our guide on implied probability and how it connects directly to finding value bets.