Vig (also known as the bookmaker's margin) is an invisible cost that determines whether you end up profitable or lose money in the long run. Every bet you place already gives a portion of your potential winnings to the bookmaker, even though most bettors don’t realize it.
Key Points - The bookmaker’s vig is the main reason why betting is unprofitable over time. - You can calculate the margin in under a minute by knowing the odds for all possible outcomes. - Even a small vig can cost you thousands of crowns annually.
How Vig (Bookmaker’s Margin) Works A bookmaker never offers odds based on true probabilities. They always adjust them in their favor. That difference is the vig.
Imagine an NHL game where the odds for both the home and away team to win are 2.00. This corresponds to a 50% probability for each team (1/2.00 = 0.5).
If the bookmaker were fair, the sum of these probabilities would be 100% (0.5 + 0.5). But in reality, you might get odds of 1.91 on both teams. Calculation: 1/1.91 = 0.5246. Sum: 0.5246 + 0.5246 = 1.0492 or 104.92%.
That "excess" 4.92% is the vig, exactly what the bookmaker collects long-term from every crown wagered.
How to Calculate Vig – A Concrete Example Simply take all the listed odds for an event, invert them (1/odds), and sum them up. Multiply the result by 100 and subtract 100. You get the exact margin in percent.
For example: - Odds: 1.91 vs 1.91 - 1/1.91 = 0.5246 (rounded) - 0.5246 + 0.5246 = 1.0492 - 1.0492 × 100 = 104.92 - 104.92 − 100 = 4.92% vig
For three-way markets (e.g., soccer: win/draw/lose), proceed the same way. Most common sportsbooks hold a vig of 4–7%, often higher on live bets. You lose on every bet regardless of how the match unfolds.
Why Vig Destroys Profit Even for Experienced Bettors Even if you tip with a 52% success rate on 2.00 odds (implied probability 50%), you can still be at a loss if the vig is 4–5%. In practice, you must overcome not only randomness but also this built-in disadvantage.
Example: You bet 1000 CZK weekly with a 5% vig. Annually, this costs you 2600 CZK, even if you hit exactly the "fair" odds. The bookmaker is always ahead. Betting without knowing the vig is like playing poker blindfolded.
Conclusion Vig is the main reason most bettors lose in the long run, even when betting sensibly. Calculate it on every ticket. Use odds comparison, value bets, and seek lower margins, or you start at a disadvantage.
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