Vig Calculator: Bookmaker Margin Analysis
The vigorish (commonly called "vig" or "juice") is the commission that bookmakers build into their odds to guarantee profit regardless of the outcome. This calculator helps you understand how bookmakers extract profit from sports betting and why bettors face a mathematical disadvantage similar to the house edge in casino games.
Understanding vig is essential for anyone researching sports betting, including Korea's Sports Toto system, where legal sports betting operates under government oversight. Just as casinos maintain profitability through house edge, bookmakers ensure consistent profits through vigorish built into every betting line.
Calculate Vig from Two-Way Betting Odds
Enter odds for a two-outcome event (e.g., moneyline, over/under, point spread).
Vig Analysis Results
| Outcome | Offered Odds | Implied Prob | True Prob | Fair Odds |
|---|---|---|---|---|
| Outcome 1 | -- | -- | -- | -- |
| Outcome 2 | -- | -- | -- | -- |
Calculate Vig from Three-Way Betting Odds
Enter odds for a three-outcome event (e.g., soccer match: Win/Draw/Loss).
Three-Way Vig Analysis
| Outcome | Offered Odds | Implied Prob | True Prob | Fair Odds |
|---|---|---|---|---|
| Home Win | -- | -- | -- | -- |
| Draw | -- | -- | -- | -- |
| Away Win | -- | -- | -- | -- |
Calculate Vig from Multiple Outcomes
Enter decimal odds for events with 2-10 possible outcomes (e.g., tournament winner, multi-horse races).
Multi-Outcome Vig Analysis
| Outcome | Offered Odds | Implied Prob | True Prob | Fair Odds |
|---|
What Is Vigorish (Vig)?
Vigorish, commonly known as "vig" or "juice," is the commission that bookmakers charge for accepting bets. It's the sports betting equivalent of the casino's house edge. By setting odds that imply probabilities totaling more than 100%, bookmakers guarantee profit regardless of which outcome wins.
The term "vigorish" derives from the Yiddish word "vyigrysh" meaning "winnings" or "profit." According to the Merriam-Webster Dictionary, it entered American English in the early 20th century through gambling circles. Today, understanding vig is essential for anyone studying sports betting mathematics or gaming regulations.
The Standard -110 Vig Explained
In American sports betting, the standard line for point spreads and totals is -110 on both sides. This means:
- You must wager $110 to win $100
- The implied probability is 52.38% (110 ÷ 210)
- Both sides sum to 104.76% implied probability
- The 4.76% excess is the bookmaker's vigorish
- Bookmaker's expected profit: ~4.55% of total wagered
How Bookmakers Calculate Odds
Professional bookmakers employ sophisticated models to estimate true probabilities for sporting events. They then adjust these probabilities to create odds that include their profit margin. The process involves:
- Probability Assessment: Statistical models estimate each outcome's true likelihood
- Margin Application: Bookmakers add their profit margin (vig) to these probabilities
- Odds Conversion: Adjusted probabilities convert to offered odds
- Line Movement: Odds adjust based on betting action to balance risk
Research from the Journal of the American Statistical Association demonstrates that while bookmaker odds are efficient predictors of outcomes, the built-in vig ensures systematic profitability regardless of prediction accuracy.
Vig Calculation Formulas
Understanding the mathematics behind vigorish helps reveal how bookmakers maintain their edge.
Vig Comparison by Market Type
Different betting markets carry different levels of vigorish. Generally, more popular and liquid markets have lower vig due to competition.
| Market Type | Typical Vig Range | Notes |
|---|---|---|
| NFL Point Spreads | 4.5% - 5% | Most liquid market, competitive pricing |
| Soccer 1X2 (Major Leagues) | 5% - 8% | Three outcomes increase margin room |
| Sports Toto Korea | 15% - 25% | Government monopoly, higher margins |
| Horse Racing | 15% - 20% | Pari-mutuel takeout varies by track |
| Props/Specials | 6% - 10% | Less liquidity, higher margins |
| Live/In-Play Betting | 6% - 12% | Risk premium for rapid odds changes |
Sports Toto and Korean Legal Betting
Sports Toto is South Korea's only legal sports betting option for Korean citizens. Operated by the Korea Sports Promotion Foundation under government oversight, Sports Toto carries significantly higher vigorish than international betting markets due to its monopoly status and regulatory requirements.
Sports Toto Margin Structure
The Korean government mandates that Sports Toto maintain specific takeout rates to fund sports development programs. The Korea Sports Promotion Foundation (KSPO) allocates betting revenue as follows:
- Prize payouts: ~50-60% of total wagers
- Sports development fund: ~20-25%
- Operating costs and government allocation: ~15-30%
This results in an effective vig of 40-50%—far higher than competitive international markets.
The high margins in Sports Toto reflect policy priorities rather than market competition. As detailed in our Korean gambling law overview, the government restricts gambling to protect citizens from exploitation while channeling any gambling activity through controlled channels that fund public programs.
Why Vig Makes Long-Term Profit Impossible
Just as the house edge guarantees casino profits, vigorish ensures bookmakers win over time. Even skilled bettors who correctly predict outcomes more often than average must overcome the vig before profiting.
Break-Even Win Rate at -110 Odds
To break even with standard -110 odds on both sides, a bettor must win:
- 52.38% of bets just to break even
- To profit 5% on wagers, win rate must exceed 54%
- To profit 10% on wagers, win rate must exceed 56%
Research published by National Institutes of Health studies shows that maintaining win rates above 53% over thousands of bets is extremely rare, with most recreational bettors winning 48-50% of their bets.
Implications for Bettors
Understanding vig provides crucial insights for anyone considering sports betting:
- Mathematical Disadvantage: Every bet carries a built-in cost regardless of outcome
- Line Shopping Value: Finding better odds reduces but never eliminates the vig
- Volume Amplifies Losses: More bets mean more vig paid to bookmakers over time
- Entertainment Perspective: Like casino gaming, sports betting is best viewed as paid entertainment
Use our Budget Calculator to plan responsible entertainment spending that accounts for the mathematical costs of betting, or explore our Risk of Ruin Calculator to understand long-term bankroll survival probabilities.
Connection to Other Gambling Mathematics
Vigorish operates on the same mathematical principles as casino house edge. Whether you're playing blackjack at Kangwon Land or placing bets through Sports Toto, the gambling operator maintains a systematic advantage through odds that favor the house.
Explore our related educational tools:
- House Edge Calculator - Calculate casino game expected losses
- Odds Converter - Convert between decimal, fractional, and American odds
- Probability Calculator - Understand true odds and expected value
- Parlay Calculator - See how vig compounds in multi-leg bets
- Bet Comparator - Compare different bets side-by-side
- Sports Toto Expected Value Calculator - Calculate expected value for Korea's legal betting with take rate analysis
Important Notice
This calculator is provided for educational purposes only. It demonstrates how bookmakers profit from sports betting through vigorish and should not be used to develop betting strategies. All forms of gambling carry risk of financial loss.
In South Korea, most sports betting is illegal for Korean citizens except through Sports Toto. Participating in unauthorized gambling can result in criminal penalties as detailed in our enforcement section.
If you or someone you know has a gambling problem, seek professional help. Visit our responsible gambling resources page or contact the National Council on Problem Gambling.
Educational Purpose
This tool is provided solely for educational purposes to help individuals understand the mathematical principles underlying sports betting odds. It is not intended to promote gambling activities or suggest that betting is a wise financial decision. The calculations demonstrate why bookmakers are profitable businesses and why bettors should expect to lose money over time.
For comprehensive information about gambling in South Korea, explore our complete collection of articles or browse our full suite of educational tools.