Margin Betting Calculator

Overround on a two-way market and implied probabilities.

Please enter valid odds
Please enter valid odds
Please enter a valid stake amount
Results
Bookmaker Margin --
Implied Probability 1 --
Implied Probability 2 --
Payout if Outcome 1 Wins --
Payout if Outcome 2 Wins --

How to Use This Calculator

  1. Set the odds format (Decimal, Fractional, or American)
  2. Input the odds for both outcomes
  3. Optionally add a stake to preview the payouts
  4. Read 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

Define bookmaker margin.

Margin (also overround or vigorish) is the percentage by which the summed implied probabilities of all outcomes exceed 100%. It is the bookmaker’s expected profit when liability is balanced. A 5% margin means the book expects to retain $5 of every $100 staked over time.

How does this differ from the hold calculator?

Both measure the same thing. This tool stresses the practical side: enter a stake and see exactly what each outcome returns. The hold calculator leans analytical, highlighting fair (no-vig) odds for comparing bookmakers.

Which books carry the lowest margins?

Sharp Asian books (Pinnacle, Sbobet) have historically held 2-3% on top markets. European recreational books usually sit at 5-8%. Promotional or niche markets can top 15%.

Why does margin drive long-term profit?

Margin is the headwind on every bet. To break even at a 5% margin you must win above the implied break-even rate. Lower-margin books make finding value bets mechanically easier.