Hold / Overround Calculator
Back to the calculator.
What is overround (hold)?
Overround (or hold) is the extra probability baked into a bookmaker’s prices. If you invert each price and add the probabilities, a fair market would sum to exactly 100%. Anything above 100% is margin. This calculator removes that margin and returns no-vig probabilities you can feed into staking or EV tools.
Overround
Margin
Fair prob A/H
Fair prob B/D
Overround = sum of inverted odds. Margin = overround − 1. Fair probabilities are each inverted odd divided by overround.
How to use this calculator
- Select Market: 2-way or 1X2.
- Choose Odds format (Decimal, American, Fractional) and enter the posted odds for each outcome. You can switch formats at any time — inputs convert automatically.
- Results update instantly:
- Overround = Σ(1/odds). Displayed as %.
- Margin = overround − 1 (also %).
- Fair probabilities = (1/odd) ÷ overround for each outcome.
- Switch between 2-way and 1X2 at any time; fields you don’t need can be left blank.
1/1.62 + 1/2.45 ≈ 1.0254 → 102.54%.
Margin ≈ 2.54%. Fair p(A) = (1/1.62)/1.0254 ≈ 0.6020 (60.20%),
fair p(B) ≈ 39.80%.
Tip: use this to check how “fat” a market is and to derive no-vig probabilities you can feed into other tools.
FAQ
Is “hold” the same as “overround”?
Yes — different terms for the same thing: the amount above 100% when you sum implied probabilities from the posted prices.
Can I paste American or fractional odds?
Yes. Use the Odds format switcher and type +120 / -110 or fractions like 10/11.
Why don’t fair probabilities sum to exactly 100% sometimes?
Display rounding. Internally the calculator uses full-precision decimals; the UI rounds to two decimals.
What’s a “good” market margin?
It depends on the sport and bookmaker. Sharper markets are often near 101–103% (2-way); softer markets can be much higher.