Odds & probability
No-Vig Calculator
Remove the market overround from a two-outcome price and compare fair probabilities.
How to read your result
Market overround is how far the two implied probabilities add up above 100%. It is a property of the quoted prices, not the sportsbook’s realized profit.
At −120 and +100, the overround is 4.55%. Proportional normalization gives fair probabilities of about 52.17% and 47.83%.
Formula and assumptions
Convert each price to an implied probability. Overround = pA + pB − 1. Fair probability for A = pA ÷ (pA + pB), and likewise for B. This assumes two mutually exclusive, exhaustive outcomes with the same settlement rules. Other margin-removal methods can give different estimates.