What Is Overround?
Overround (also called vig, juice, or margin) is how bookmakers guarantee profit. It's the percentage by which the implied probabilities of all outcomes exceed 100%.
In a fair coin flip, each side has 50% probability. Fair odds would be 2.00 for both. But bookmakers might offer 1.91 for each, implying 52.4% + 52.4% = 104.8%. The 4.8% is the margin.
This margin ensures the bookmaker profits regardless of outcome. If they take equal money on both sides at 1.91 odds, they pay out 95.5% and keep 4.5%.
Calculating and Comparing Margins
To calculate overround: sum the implied probabilities of all outcomes and subtract 100%. For a three-way market (1X2): add the implied probabilities of home win, draw, and away win.
Margins vary significantly between bookmakers and markets. Sharp bookmakers like Pinnacle might offer 2-3% margins, while recreational bookmakers might charge 6-10%.
Betting at lower margin bookmakers significantly improves your long-term results. Even a 2% difference in margin compounds to substantial savings over hundreds of bets.
Shopping for the Best Odds
Smart bettors compare odds across multiple bookmakers for every bet. This practice, called line shopping, ensures you always get the best price available.
The difference between 2.00 and 2.10 odds might seem small, but it's a 5% improvement in potential profit. Over your betting career, this adds up to significant extra returns.