Betting Odds Formats Explained: Decimal, American and Fractional

Canadian sportsbooks display the same bet in three different formats depending on the site and the sport. The underlying probability is identical; only the notation changes. Knowing how to read each one makes it possible to compare prices across operators.

Decimal odds

Decimal odds show the total return per dollar staked, including the stake. A price of 2.50 returns $2.50 for every $1 wagered, so a $20 bet pays $50 in total and $30 in profit. This is the default format on most Canadian and European sites, and the easiest for arithmetic.

American odds

American odds use a plus or minus sign around a base of 100. A line of +150 means a $100 stake wins $150 in profit. A line of -200 means a bettor must risk $200 to win $100. The favourite carries the minus sign, the underdog the plus. Hockey and basketball markets on North American sites often default to this format.

Fractional odds

Fractional odds such as 5/2 show profit relative to stake: win five units for every two risked. They are common in horse racing and on UK-oriented sites. To convert to decimal, divide the fraction and add one: 5/2 becomes 2.5 + 1 = 3.50.

Turning odds into probability

• Decimal: divide 1 by the odds. 2.50 implies a 40% chance.
• American minus: divide the line by the line plus 100. -200 implies 66.7%.
• American plus: divide 100 by the line plus 100. +150 implies 40%.

Adding up the implied probabilities of every outcome in a market gives a figure above 100%. The excess is the bookmaker’s margin, and it is the single most useful number for judging whether a line is competitively priced.