Devig methods

Remove the bookmaker margin

Decimal odds imply probabilities of 1 divided by odds. Devig methods remove the overround from a complete two-way or three-way market.

Four methods

• Multiplicative divides implied probabilities by their sum.
• Additive subtracts an equal share of the margin from each outcome.
• Power finds k so the sum of implied probabilities raised to k equals 1.
• Shin solves for the insider-trading parameter z so fair probabilities sum to 1.

Worst case

Worst case takes the highest fair odds for each outcome across the four methods. It is a conservative envelope, not a normalized market. For extreme prices additive may be invalid; standard Shin is not available for negative margins. The free calculator labels these cases instead of inventing values.