Basketball Odds Explained: Decimal, American and the Margin
A basketball bet is only as clear as the price attached to it, and Canadian sportsbooks show that price in either decimal or American format, sometimes letting you switch between the two.
Reading either one comes down to one idea: the number tells you how much a winning bet returns, and everything else, implied probability, converting between formats, the margin built into the price, follows from that. This page covers both formats, how to convert between them, what implied probability means, and why a price that looks close to even on both sides still isn’t a true 50/50. Nothing here quotes a live number as Rexbet’s own; every example is marked as illustration only, since a real price changes constantly.
Decimal Odds
Decimal odds are the more literal of the two formats: multiply your stake by the number shown and that’s your total return, including your original stake. Say the Boston Celtics are priced at a decimal 1.65 to beat the Charlotte Hornets, for illustration only, that returns $16.50 on a $10 bet, $6.50 profit plus the $10 you staked back.
Anything below 2.00 returns less than double your stake and marks the favoured side; anything above 2.00 marks the underdog. Decimal is common across most of the world outside the United States, and that’s part of why it’s the default on many Canadian-facing sportsbooks.
American Odds
American odds show the same information as a plus or minus number attached to 100. That same Celtics price shows as -154 in American odds, for illustration only: a minus number is how much you’d need to stake to win $100, so a $154 stake wins $100 profit.
The Hornets on the other side price out at +140, a plus number instead, showing what a $100 stake would win, in this case $140 profit. The minus side is always the favourite, the plus side always the underdog: American odds let you spot which side the market favours at a glance, before you convert anything.
Converting Between the Two
Converting decimal to American, and back, is mechanical rather than intuitive at first. Start with which side of 2.00 the price sits on. Above 2.00, an underdog price, subtract 1 from the decimal and multiply by 100 for the plus number: the Hornets’ 2.40 becomes (2.40 − 1) × 100 = +140, the same underdog price used above. Below 2.00, a favourite price, subtract 1 from the decimal, then divide -100 by that number for the minus price: the Celtics’ 1.65 becomes -100 ÷ (1.65 − 1) = -154, the same favourite price used above.
Neither conversion changes what the bet actually pays, it’s the same price described two different ways, and a sportsbook offering only one format hasn’t priced the bet any differently than one offering both. For a closer look at which format Canadian sportsbooks tend to default to and why, see Decimal vs American Odds Explained.
Implied Probability
Implied probability is the percentage chance of an outcome that a given price represents, found by converting the odds themselves, useful for comparing two different-looking prices on equal footing.
For decimal odds, implied probability is 1 divided by the decimal price; for American odds, the formula differs slightly depending on whether the number is plus or minus. The Celtics’ 1.65 favourite from above implies a 60.6% chance, for illustration only; the Hornets’ 2.40 underdog price implies a lower 41.7%, exactly what you’d expect from 1.65 being the shorter, more heavily favoured price of the two.
Add the Celtics’ 60.6% to the Hornets’ 41.7% and the total comes to 102.3%, not 100%.
That extra 2.3% doesn’t belong to either team, it’s the sportsbook’s margin, priced into both sides of the same bet.
Example only, not a live line. Illustrates how decimal and American odds describe the same price.
The Margin Built Into a Two-Way Price
If you add up the implied probabilities of both sides of a two-way bet, a spread or a moneyline priced close to even, for instance, the total comes to slightly more than 100%. That extra percentage is the margin built into the price, and it’s how a sportsbook can offer a price on both outcomes of the same event and still expect to come out ahead across enough bets, regardless of which side wins any single one.
Take a Toronto Raptors–Brooklyn Nets spread priced at -110 on both sides, for illustration only: each side implies slightly better than a 50% chance, and that overage is the margin showing up directly in the numbers. It isn’t specific to basketball, or to any one sportsbook, the same idea sits under nearly every two-way price you’ll see.
How and Why a Line Moves
A line opens based on a model plus context, then shifts as new information arrives and as money comes in on each side.
Injury news is one of the biggest single movers in the NBA, a star like Jayson Tatum listed questionable close to tip-off changes what the Celtics are expected to produce, and a lopsided amount of money on one side can move a price even without any news at all, as the sportsbook adjusts to balance its own exposure. How NBA Lines Move and What Moves Them covers this in more depth, including how a back-to-back scheduling spot factors in.
Reading Odds, Answered
What’s the actual difference between decimal and American odds?
Decimal shows your total return as a multiple of your stake; American shows it as a plus or minus number relative to a $100 bet.
Same price, two different notations, pick whichever reads more naturally to you.
How do I convert decimal odds to American odds?
For a decimal price of 2.00 or higher, subtract 1 and multiply by 100 for a plus number.
For a decimal price under 2.00, subtract 1 from the decimal, then divide -100 by that number for a minus number. Both directions describe the identical price.
Why do both sides of a two-way bet add up to more than 100%?
That gap is the sportsbook’s margin, sometimes called the vig or the juice, and every two-way bet carries one, it isn’t a Rexbet-specific markup.
In practice it means neither side of a close bet is truly priced at 50/50; both sides sit a little above it, and that sliver is what lets a book profit over enough bets no matter which side wins any single one. It’s also the reason shopping the same bet across sportsbooks can matter, a tighter margin means less of your stake goes to the book’s cut before the game even starts.
Does the odds format I choose change my payout?
No. Decimal and American are just two different ways of displaying the same price. Switching formats in your account settings changes how the number looks, not what a winning bet actually returns.
What is implied probability in sports betting?
It’s the percentage chance of an outcome that a price represents once you convert it, 1 divided by the decimal price, or the equivalent American-odds formula. It’s the easiest way to compare two prices that look different but represent a similar chance.
For how each of these prices actually applies to a specific bet, moneyline, spread, totals and the rest, see the full Bet Types Explained breakdown.