Reviewed by TipsterCheck Editorial TeamLast checked 29 October 2026MethodologyCorrections
Betting glossary · Odds & Maths
What is Implied Probability?
What is Implied Probability?
How implied probability works
Every set of odds can be converted into a percentage that represents how likely the bookmaker believes an outcome to be. For decimal odds, the formula is straightforward: divide 1 by the decimal odds and multiply by 100. So odds of 2.50 give an implied probability of 1 ÷ 2.50 × 100 = 40%. For fractional odds, add the denominator to the numerator, then divide the denominator by that total and multiply by 100. Odds of 3/1 become 1 ÷ (3+1) × 100 = 25%.
The crucial point is that bookmakers build a profit margin — known as the overround — into their prices, so the implied probabilities across all outcomes in a market will sum to more than 100%. A two-outcome market might show implied probabilities of 52% and 54%, totalling 106%. That extra 6% is the bookmaker's edge. True probability and implied probability are therefore not the same thing; implied probability already has the margin baked in.
A worked example
Suppose a football match is priced at: Home win 2.10, Draw 3.40, Away win 3.80. Converting each: Home = 47.6%, Draw = 29.4%, Away = 26.3%. These sum to 103.3%, meaning the overround is roughly 3.3%. To find the fair, margin-free probability for each outcome, you would divide each implied probability by that total — giving 46.1%, 28.5%, and 25.5% respectively.
If you believe the home side's true chances are closer to 55%, the offered price of 2.10 (implied 47.6%) looks potentially undervalued. That gap between your assessed probability and the bookmaker's implied probability is the starting point for identifying a value bet.
Why it matters when judging a tipster
When reviewing a tipster's track record on TipsterCheck, implied probability helps you assess whether their advised prices genuinely represented value at the time the tip was issued. A tipster who consistently backs selections where their assessed probability exceeds the implied probability is demonstrating a disciplined, evidence-based approach. One who simply backs favourites at short implied probabilities faces a much steeper climb to generate long-term profit.
Implied probability also sits at the heart of closing line value (CLV) analysis. If a tipster's selections are repeatedly advised at odds with a lower implied probability than the final market price, that suggests the market moved in their favour — a strong indicator of genuine predictive edge. Without understanding implied probability, it is difficult to distinguish a tipster who has been lucky from one who has a repeatable skill.
Example: A tipster advises a team at 3.00 (implied probability 33.3%); if you assess their true chance at 40%, the bet carries positive expected value and the advised odds represent a potential value opportunity.
FAQs
How do I convert fractional odds to implied probability?
Add the two numbers together, divide the denominator by that total, then multiply by 100. For example, 5/2 becomes 2 ÷ (5+2) × 100 = 28.6%. This figure includes the bookmaker's margin.
Is implied probability the same as true probability?
No. Implied probability includes the bookmaker's overround, so it overstates the perceived chance of each outcome. True probability, once the margin is removed, will be slightly lower for each selection in the market.
Why do implied probabilities in a market add up to more than 100%?
The excess above 100% represents the bookmaker's built-in margin or overround. It ensures the bookmaker expects a profit regardless of which outcome occurs, assuming balanced book positions.
More odds & maths terms: Odds-Against, Odds-On, Push