Odds Explained

Odds can look like three different languages: 2.50 on one site, 3/2 on another, +150 on a third. In fact they are the same price written three ways. Once you can read all of them, you can see what a bet pays, what chance the price implies and how much the bookmaker has built in for itself. All the examples on this page use made-up numbers.

Decimal odds

Decimal odds show the total return for every 1 unit staked, including your stake. At 2.50, a 10-unit bet returns 25 if it wins: 15 profit plus the original 10. Anything below 2.00 means the profit is smaller than the stake; anything above means it is larger. This format is the easiest for quick maths, which is why we use it most on this site.

Fractional odds

Fractional odds show the profit relative to the stake. 3/2 means you win 3 for every 2 you bet, so 10 units at 3/2 brings 15 profit and 25 back in total, exactly matching 2.50 in decimal. "Evens" is 1/1. When the first number is smaller, as in 1/2, the profit is less than the stake.

American odds

American, or moneyline, odds work from a base of 100:

• A plus number shows how much profit a 100-unit stake would make. +150 means 100 wins 150.
• A minus number shows how much you must stake to make 100 profit. -200 means you risk 200 to win 100.

Quick conversion table

Implied probability

Every price hides a percentage. With decimal odds, divide 1 by the price: 1 / 2.50 = 0.40, or 40%. That is the chance the bet needs to win, in the long run, simply to break even. If you believe the true chance is lower, the price is poor value for you; if you believe it is higher, you think the price is generous. Either way, the outcome itself is still uncertain.

Spotting the margin

Here is a hypothetical football match priced at 1.80 for the home side, 3.60 for the draw and 4.50 for the away side. Convert each one:

1. Home: 1 / 1.80 ≈ 55.6%
2. Draw: 1 / 3.60 ≈ 27.8%
3. Away: 1 / 4.50 ≈ 22.2%

Together they add up to about 105.6%. A fair book would total exactly 100%, so the extra 5.6 percentage points are the bookmaker's built-in margin. That cushion is why even a bettor who guesses well tends to lose slowly over time. Our explainers on the prop bet and the round robin show how that margin carries through into specific bet types.

Three habits worth keeping

• Convert unfamiliar prices into decimal and a percentage before you decide anything.
• Remember that shorter odds are not "safe"; they only mean the loss is expected less often.
• Read the settlement rules, because a price only tells you what happens if the bet wins.

Betting is for adults only, and the forms of betting allowed differ from place to place. Understanding odds will not make you a winner, but it will make it much harder for a price to fool you.