How to Read Betting Odds: American, Decimal and Fractional
A plain guide to the three odds formats, the main bet types, and why the same bet pays differently at different sportsbooks.
The Smart Lines teamOctober 20264 min read
The three odds formats
Odds tell you two things: how much a bet pays, and how likely the sportsbook thinks it is. The same price can be written three ways.
American odds (common in the US)
- Negative (−) is the favourite: how much you stake to win $100. At −150 you stake $150 to win $100.
- Positive (+) is the underdog: how much you win on a $100 stake. At +145 a $100 bet wins $145.
- −110 is the standard price on spreads and totals: a $100 bet wins $90.91.
Decimal odds (common in Canada)
Decimal odds are your total return per $1 staked, stake included. At 1.91 a $100 bet returns $191: your $100 back plus $91 profit. Anything below 2.00 is a favourite and anything above is an underdog. Most Canadian sportsbooks, including those in Ontario, show decimal odds by default.
Fractional odds (common in the UK)
Fractional odds are profit over stake: 5/2 wins $5 for every $2 staked, the same as +250 or 3.50 in decimal.
Same price, three formats
An underdog at +150
- American
- +150
- Decimal
- 2.50
- Fractional
- 3/2
- A $100 bet returns
- $250 ($150 profit)
You can switch between formats with the odds converter. On The Smart Lines, the American / decimal toggle at the top of every page changes how all odds are shown.
What the odds say about probability
Every price implies a chance of winning: +150 implies 40%, −150 implies 60%, and decimal odds imply 1 ÷ the odds. The two sides of a bet add up to a bit more than 100%; the extra is the sportsbook’s margin. Our guide to implied probability covers the maths.
The main bet types
- Moneyline: pick the winner, at the price shown.
- Spread (point spread, run line, puck line): the favourite has to win by more than the spread, and the underdog can lose by less than it and still win the bet. Usually priced near −110 each side.
- Total (over/under): bet on whether the combined score goes over or under a number.
- Player props: bets on one player’s stats, like points, passing yards or shots on goal, usually as an over/under.
- Parlays: several bets combined, all of which must win. The payout multiplies, but so does the book’s margin; see the parlay calculator.
Why odds differ between sportsbooks
Each sportsbook sets its own prices, and they don’t move in lockstep. One book reacts to news faster, another is protecting itself against heavy action on one side, a third is offering a better price to win customers. On any given game, the price on the same bet can vary noticeably from book to book.
Line shopping
The same team at two books
Suppose a team’s fair chance of winning is 42% (fair odds of about +138). One book offers +145, another +130:
- At +145: expected value per $100
- +$2.90
- At +130: expected value per $100
- −$3.40
Same bet, opposite outcomes over the long run. Taking the best available price, called line shopping, is the simplest edge a bettor can have. See expected value for the full calculation.
The short version
- American: minus is the stake to win $100, plus is the win on $100.
- Decimal: the total return per $1. Most Canadian books use it.
- Every price implies a probability, and both sides add up to over 100%.
- The same bet pays differently at different books, so always compare.
Compare the latest prices across sportsbooks on the odds board.