The conversion
implied = 1 / decimal implied(+150) = 100 / 250 = 40.0% implied(−150) = 150 / 250 = 60.0%
Read the curve left to right: heavier favourites (−200, −400) require much higher probabilities, and each extra 100 on a long shot buys less and less probability.
What "implied" does and does not mean
Implied probability is the break-even rate of the price — what you would need to believe to call it fair. It is not the book's honest estimate of the truth, because it still contains the vig. Removing the vig gives a closer estimate of what the market actually believes; see Vig & fair odds.
Model outputs — a PBE probability, a simulation share, a Fight Model win probability — are already probabilities. Converting the price to a probability puts both numbers in the same unit so they can be compared.
Comparing a model probability with a price
- A model gives a batter a 30% chance to homer.
- The offered price is +280: implied = 100 / 380 = 26.3%.
- The gap is 3.7% points in the model's favour — if the model's 30% is right.
A 4-point gap sounds large, but a model probability of 30% can easily carry ±3–5 points of uncertainty. The EV calculator lets you enter that uncertainty and see whether the edge survives it.