Margin Tool
Bookmaker margin (overround) on a two-way market, plus implied probabilities.
How to Use This Calculator
- Pick an odds format: Decimal, Fractional, or American
- Type in the odds for both outcomes
- Add a stake if you want to see potential payouts
- Read off the bookmaker margin and the implied probabilities
Formula
Implied Probability = 1 / Decimal Odds
Bookmaker Margin (Overround) = (1 / Odds₁) + (1 / Odds₂) − 1
Payout = Stake × Decimal Odds
Margins below 5% are considered competitive; above 10% are typical of recreational books or low-liquidity markets.
Frequently Asked Questions
What is bookmaker margin?
Margin (also overround or vigorish) is the amount by which the implied probabilities of all outcomes add up past 100%. It’s the bookmaker’s expected take when liability is balanced. A 5% margin means the book expects to keep $5 out of every $100 staked over time.
How does this differ from the hold calculator?
Both measure the same thing. This one is practical: enter a stake and see what each outcome pays. The hold calculator leans analytical, highlighting fair (no-vig) odds for comparing bookmakers.
Which bookmakers run the lowest margins?
Sharp Asian books (Pinnacle, Sbobet) have historically held 2-3% on top markets. European recreational books sit around 5-8%. Promotional or niche markets can top 15%.
Why does margin matter for long-term profit?
Margin is the headwind on every bet. At a 5% margin you must win above the implied break-even rate just to stay flat. Lower-margin books make finding value mechanically easier.