Bookmaker margin calculator
Enter the decimal odds of the outcomes — two for no-draw markets, three for lines with a draw. The third field may stay empty.
Sum of implied probabilities — A fair line would sum to exactly 100%. Anything above is the price built into the odds.
Bookmaker margin — (S − 1) / S, where S is the probability sum. The share of turnover the line keeps on average.
Fair odds (no-vig) — Odds after normalising probabilities to 100% — what the line would be without commission.
The calculator uses proportional normalisation. Real margin is distributed unevenly across outcomes, especially on favourites and longshots. Verify calculations yourself.