Add up the chances
Divide 1 by each decimal price and add the results. On a fair book they would add up to exactly 100%. Whatever is above 100% is the margin the book keeps.
Shuffle priced Bayern Munich v Arsenal on 21 October 2026 at 2.29, 3.75 and 3.00. That is 43.67% + 26.67% + 33.33% = 103.67%, so Shuffle keeps a margin of 3.67%, the lowest of the eight books that priced the match.
