Overround Calculator
Calculate the bookmaker's margin on any betting market. Enter the odds for each outcome to see the overround, margin per outcome, fair odds and a rating of how competitive the market is.
Enter Market Odds
Understanding Overround
What is Overround?
Overround (also called vig or juice) is the bookmaker's built-in profit margin. In a fair market, all implied probabilities would sum to exactly 100%. A bookmaker's market always sums to more than 100% — the excess is their margin.
How It's Calculated
Add up 1/odds for every outcome and multiply by 100 to get the total implied probability. Subtract 100 to get the overround. For example: odds of 2.10 and 2.10 give implied probs of 47.6% + 47.6% = 95.2%... wait, that's under 100 — this would be a bookmaker paying out more than it takes in. Real markets always exceed 100%.
What's a Good Overround?
Exchange markets (Betfair) typically have 1–2% overround. Online bookmakers range from 3–8% on popular markets. High street bookmakers and novelty markets can exceed 15%. The lower the overround, the better value for the bettor.
Fair Odds
Fair odds are what the odds would be if the bookmaker had zero margin. They're calculated by dividing the implied probability of each outcome by the total implied probability across all outcomes. Fair odds are always higher than bookmaker odds.