Margin Helper
See the bookmaker's margin (overround) on a two-way market and the implied chances.
How to Use This Calculator
- Choose the odds format you’d like to use (Decimal, Fractional, or American)
- Enter the odds for both outcomes
- If you fancy, add a stake to preview the potential payouts
- Take a look at 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 does bookmaker margin actually mean?
Margin (you might also hear it called overround or vigorish) is the amount by which all the outcomes’ implied probabilities added together go past 100%. It’s the bookmaker’s expected profit 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 look at the very same idea. This one is the hands-on version: type in your stake and see precisely what each outcome pays out. The hold calculator leans more analytical and focuses on fair (no-vig) odds so you can compare bookmakers.
Which bookmakers tend to have the smallest margins?
Sharp Asian books (Pinnacle, Sbobet) have historically run 2-3% margins on their main markets. European recreational books usually sit around 5-8%. Promotional or niche markets can climb above 15%.
Why should I care about margin for long-term profit?
Think of margin as the headwind every bet pushes against. To break even at a 5% margin you need to win more often than the implied break-even rate. Lower-margin books simply make it mechanically easier to find value bets.