Bookmaker margin
from the line odds
2 outcomes
3 outcomes
Mathematical (overround)
—
sum of probabilities − 100%
Bookmaker's (real)
—
bookmaker's share of the bank
Mathematical margin — by how much the sum of inverse odds exceeds 100% (the classic overround).
Bookmaker margin — the real share the bookmaker keeps when stakes are spread equally across all outcomes (this is usually what bookmakers mean by the line margin; it is always smaller than the overround).
Bookmaker margin — the real share the bookmaker keeps when stakes are spread equally across all outcomes (this is usually what bookmakers mean by the line margin; it is always smaller than the overround).
Stake distribution (arbitrage)
how much to stake on each outcome so the profit is the same
2 outcomes
3 outcomes
System M of N
winnings when outcomes partly match
Odds converter
decimal ⇄ American ⇄ fractional
Enter a value in any field and the other two recalculate automatically.
Odds converter
Odds come in decimal (European, 2.50), fractional (British, 3/2) and American (+150, −200) formats. The converter turns one format into another and shows the implied probability of the outcome: 1 ÷ decimal odds.
The bookmaker's implied probability includes the margin, so the probabilities of all outcomes add up to more than 100%. You can calculate the margin in the margin calculator.