Results appear here as you type.
For information and entertainment only — not betting, financial or legal advice. Results are estimates based on your inputs.
How the Implied Probability & Margin Calculator works
Add the odds for every outcome of a market. The calculator converts each price to a probability, adds them up and shows how far the total is above 100% — that excess is the overround, the margin built into the prices. It then rescales the probabilities to give “fair” odds with the margin removed.
Formula
- Implied probability = 1 ÷ decimal odds
- Overround = (sum of implied probabilities − 1) × 100%
- Fair probability = implied probability ÷ sum of implied probabilities
- Fair odds = 1 ÷ fair probability
Worked example
A two-way market at 1.91 / 1.91 implies 52.4% + 52.4% = 104.7%. The overround is 4.7% and the fair price of each side is 2.00.
Frequently asked questions
What is a good overround?
Lower is better for the bettor. Major two-way markets are often 2–5%, while outright and novelty markets can be much higher.
Does removing the margin tell me who will win?
No. Fair odds only strip out the operator margin; they are still an estimate by the market, not a prediction.
Play responsibly
Calculators describe maths, not outcomes. Gambling is for adults aged 18+ and can be addictive — set limits and never stake money you cannot afford to lose.