Implied Probability and Overround Calculator
Shows what odds imply, and how far a market adds up past 100%.
Implied probability of selection 1
— %
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Total of all selections — %
Overround — %
Bookmaker’s margin — %
Each selection
Reading this —
The formula
implied probability = 1 ÷ decimal odds overround = sum of implied probabilities − 100% margin = 1 − 1 ÷ (sum of implied probabilities)
Removing the margin here scales every selection down in proportion. It is an approximation, because bookmakers do not spread their margin evenly.
What to watch out for
Implied probability is what the price says, not the true chance of the event. Each field accepts decimal, fractional or American odds.
Frequently Asked Questions
What probability do odds of 2.50 imply?
40.00%.
What is the overround on 2.10, 3.40 and 3.60?
4.81%, with a margin of 4.59%.