Calculate Bookmaker Margin
Margin (overround) on a two-way market and implied probabilities.
How to Use This Calculator
- Tap your odds format (Decimal, Fractional, or American)
- Drop in the odds for both outcomes
- Add a stake if you want to preview the payouts
- Get the bookmaker margin and 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 does bookmaker margin mean?
Margin (a.k.a. overround or vigorish) is how far the combined implied probabilities of every outcome push past 100%. It’s the bookmaker’s expected take when their liability is balanced. A 5% margin means they expect to keep $5 out of every $100 staked over time.
How is this different from the hold calculator?
Both measure the same thing. This one keeps it practical: punch in a stake and see exactly what each outcome returns. The hold calculator leans analytical, spotlighting fair (no-vig) odds for stacking bookmakers side by side.
Which bookmakers run the leanest margins?
Sharp Asian books (Pinnacle, Sbobet) have historically held 2-3% on top markets. European recreational books usually sit at 5-8%. Promo or niche markets can blow past 15%.
Why does margin matter for long-term profit?
Margin is the headwind on every single bet. To break even at a 5% margin you have to win above the implied break-even rate. Lower-margin books just make finding value bets mechanically easier.