Bookmakers never play fair. Vig, or margin, is their guaranteed profit. Every ticket is a few percentage points worse for you than it appears.
Key Points - Vig is a hidden fee embedded in every odds. - High vig destroys long-term profit potential. - Correct margin calculation is fundamental for value betting.
What is vig and how does it work Every odd includes the bookmaker’s margin. This gives the bookmaker an edge even if half the bettors wager on each side. Vig is the difference between the true probability and what the odds imply.
Typically, vig ranges between 3–8%. It tends to be lower in major leagues and higher in smaller competitions. The higher the vig, the lower your chance of profit.
How to calculate vig (bookmaker margin) The basic formula is simple. Take all the odds offered for a market event, calculate their reciprocals (1/odds), and sum them up. Subtract the result from 1 and multiply by 100 to get the percentage margin.
Example: NHL match. The bookmaker offers 2.00 for the home team, 1.80 for the away team. Implied probabilities: 1/2.00 = 0.50 (50%), 1/1.80 = 0.555 (55.5%). Sum: 105.5%. Vig = (1.055–1) × 100 = 5.5%.
Why vig destroys long-term profit If you bet on odds with high vig, you will lose in the long run. Even if you win 50% of bets at even odds of 2.00, you lose due to the margin. The bookmaker never offers true value; they always take a cut.
If you find odds with lower vig, or even negative vig (so-called “overround below 100%”), you theoretically have a value bet. But this is extremely rare. Most bettors lose long-term precisely because of vig.
Practical impact of vig on your bankroll If you consistently bet on odds with a 5% vig, you theoretically lose 5% of your turnover. With 100 bets of 1000 CZK each, that’s 5000 CZK lost "for nothing." It’s better to seek low-vig opportunities or bet where vig is minimal.
Want to know where vig is lowest? Follow odds comparison sites or use analytical tools like Slyx. A complete breakdown of value betting can be found in other articles.
The bookmaker’s margin is the invisible opponent of every bettor. Those who ignore it pay more in the long run than necessary. Bet responsibly and only if you are 18+.