Odds tell you two things: how much you win and how likely the bookmaker thinks it is. 5/2 means you win £5 for every £2 you stake. As a percentage, 5/2 is a 28.6% chance.
Fractional odds
Fractional odds are the UK standard, especially in horse racing. The first number is what you win. The second is what you stake. So 5/2 pays £5 profit for every £2 you bet, and you get your stake back too.
- £2 at 5/2 returns £7: £5 profit plus your £2.
- £10 at 4/1 returns £50: £40 profit plus your £10.
- £10 at 1/2 returns £15: £5 profit plus your £10.
When the first number is bigger, the selection is an outsider. When the second number is bigger, it's "odds on" and you win less than you stake. Evens, written 1/1 or evs, pays the same as you stake.
Decimal odds
Decimal odds show the total return for every £1, stake included. That makes them quicker to work with. Multiply your stake by the decimal and you have your return.
- 5/2 is 3.5, so £10 returns £35.
- Evens is 2.0, so £10 returns £20.
- 1/2 is 1.5, so £10 returns £15.
To turn fractional odds into decimal, divide the top number by the bottom one and add 1. 7/4 becomes 1.75 plus 1, which is 2.75.
American odds
You'll see these on US sports. A plus number is the profit on a $100 stake, so +250 is the same as 5/2. A minus number is what you have to stake to win $100, so -200 is the same as 1/2.
Turning odds into a percentage
Divide 1 by the decimal odds. That's the implied probability, the chance of winning the price suggests.
| Fractional | Decimal | Implied chance |
|---|---|---|
| 1/2 | 1.50 | 66.7% |
| Evens | 2.00 | 50.0% |
| 6/4 | 2.50 | 40.0% |
| 2/1 | 3.00 | 33.3% |
| 5/2 | 3.50 | 28.6% |
| 4/1 | 5.00 | 20.0% |
| 10/1 | 11.00 | 9.1% |
Where the bookmaker makes its money
Add up the implied chances of every outcome in a market and you'll get more than 100%. The extra is the bookmaker's margin, sometimes called the overround.
| Outcome | Odds | Implied chance |
|---|---|---|
| Home win | 6/4 (2.50) | 40.0% |
| Draw | 12/5 (3.40) | 29.4% |
| Away win | 2/1 (3.00) | 33.3% |
| Total | 102.7% |
In this example the total is 102.7%. That 2.7% is roughly what the bookmaker expects to keep if money comes in evenly on all three outcomes. It's why most people lose over time, even when they pick plenty of winners.
Questions people ask
How do betting odds work?
Odds show what you win compared with what you stake, and how likely the bookmaker thinks the result is. 5/2 pays £5 profit for every £2 staked and implies a 28.6% chance.
What does 11/10 mean?
You win £11 for every £10 you stake. In decimal it's 2.1, so £10 returns £21.
Are decimal or fractional odds better?
Neither pays more. They're two ways of writing the same price. Decimal is easier to compare and multiply, which is why exchanges use it.
What does odds on mean?
The bookmaker thinks it's more likely to happen than not. You win less than you stake, for example 1/2.