Betting Odds Explained: Decimal, American & Fractional

Odds are just a way of expressing probability and payout. There are three common formats — decimal, American and fractional — and once you can read all three (and convert between them), the whole betting world opens up. Here's the plain-English version.

Decimal odds

The standard in Europe and for sharp bettors. The number is your total return per unit staked, including your stake. Odds of 2.50 mean a €10 bet returns €25 (€15 profit + your €10 back). Simple to compare: higher = bigger payout.

American (moneyline) odds

Common in the US. A positive number (+150) is the profit on a 100 stake; a negative number (−200) is the stake needed to profit 100. So +150 = bet 100 to win 150; −200 = bet 200 to win 100.

Fractional odds

Traditional in the UK. 3/2 means you win 3 for every 2 staked (plus your stake back). It's the same as decimal 2.50 — just written as a ratio of profit to stake.

Implied probability

Every price implies a break-even probability: implied % = 1 / decimal odds. So 2.00 implies 50%, 1.50 implies 66.7%, 5.00 implies 20%. This is the number that actually matters — if your estimate of the true chance is higher than the implied probability, the bet has positive expected value.

Converting between formats

You'll constantly need to jump between formats — a US source quotes −110, your book shows 1.91, a UK tipster says 10/11. Rather than do the maths each time, use our free odds converter: type a price in any format and get all the others plus the implied probability instantly.

The next step: fair odds

Implied probability includes the bookmaker's margin. To find real value you want the no-vig probability — the fair price with the margin removed. Learn how in What Is the Vig?, or jump straight to the no-vig calculator.