How to read betting odds: decimal, fractional and American
Sport Predict · 1 min read
Odds tell you two things: how likely the bookmaker thinks something is, and how much you get back if your bet wins. The same price can be written three ways, and you can switch between them with the odds selector at the top of our site.
Decimal odds
Decimal odds, common in Europe and Australia, show your total return for every 1 unit staked, including the stake. A £10 bet at 2.50 returns £25: £15 profit plus your £10 back. Anything below 2.00 is “odds-on”, meaning the outcome is seen as more likely than not.
Fractional odds
Fractional odds are traditional in the UK and Ireland. They show profit relative to stake. At 6/4 you win £6 for every £4 staked, so a £10 bet returns £15 profit plus your £10. Evens (1/1) doubles your money. When the first number is smaller than the second, as in 4/6, the selection is odds-on.
American odds
American odds use a plus or minus sign. A plus number shows profit on a $100 stake: +150 wins $150. A minus number shows how much you need to stake to win $100: −200 means staking $200 to win $100. Underdogs have plus prices, favourites minus.
Converting between formats
| Decimal | Fractional | American |
|---|---|---|
| 1.50 | 1/2 | −200 |
| 1.91 | 10/11 | −110 |
| 2.00 | 1/1 (evens) | +100 |
| 2.50 | 6/4 | +150 |
| 3.00 | 2/1 | +200 |
| 5.00 | 4/1 | +400 |
Implied probability
Every price implies a probability. For decimal odds, divide 1 by the odds: 2.50 implies 40%, 1.50 implies 67%. Add up the implied probabilities of all outcomes in a market and you will get more than 100%. The extra is the bookmaker’s margin, sometimes called the overround or vig.
Why this matters
A bet only has value if your estimate of the probability is higher than the one implied by the odds. That is why our previews always show our own probabilities next to the price: if we rate a team at 55% and the odds imply 48%, that gap is the reason for the pick. If the gap disappears, so does the value.