Margin Calculator
Calculate the bookmaker's margin (overround) on a two-way market and see implied probabilities and potential payouts for any stake.
How to Use This Calculator
- Select your odds format (Decimal, Fractional, or American)
- Enter the odds for both outcomes
- Optionally enter a stake to see the potential payouts
- View 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 is bookmaker margin?
Margin (also called overround or vigorish) is the percentage by which the sum of implied probabilities of all outcomes exceeds 100%. It represents the bookmaker’s expected profit if liability is balanced. A 5% margin means the bookmaker expects to keep $5 of every $100 staked over time.
How does the margin calculator differ from the hold calculator?
Both quantify the same concept. This calculator focuses on the practical impact: enter your stake and see exactly what each outcome pays. The hold calculator is more analytical and emphasises fair (no-vig) odds for comparing bookmakers.
Which bookmakers have the lowest margins?
Sharp Asian books (Pinnacle, Sbobet) historically run 2-3% margins on top markets. European recreational books typically run 5-8%. Promotional or niche markets can exceed 15%.
Why does margin matter for long-term profit?
Margin is the headwind every bet faces. To break even at a 5% margin you need to win above the implied break-even rate. Lower margin books make it mechanically easier to find value bets.