Fractional odds explained
How to read fractional odds such as 5/2, evens and odds-on prices, work out the return on a stake and convert them to decimal or American odds.
Fractional odds are the traditional way of writing prices in the UK and Ireland, and you will still see them on racing and football there. A fractional price tells you how much profit a winning bet makes compared with the stake. Once you can read one, converting it to decimal or American odds takes seconds, and OddsKeepr can show every price as a fraction if that is the format you know best.
How to read a fractional price
A fractional price is written as two numbers with a slash, such as 5/2, and is read "five to two". The first number is the profit; the second is the stake that earns it.
- At
5/2, every 2 you stake makes 5 profit if the bet wins. - At
1/2, every 2 you stake makes 1 profit. - At
10/3, every 3 you stake makes 10 profit. Some sportsbooks write the same price as100/30.
The return on a winning bet is the profit plus your stake back. The formula is:
Return = stake × (first number ÷ second number) + stake
Worked example: 5/2
You stake 10 at 5/2.
- Profit: 10 × 5 ÷ 2 = 25
- Return: 25 + 10 = 35
If the bet loses, you lose the 10.
Evens
Evens, also written 1/1 or "even money", means the profit equals the stake. A stake of 10 makes 10 profit and returns 20. It implies a 50% chance and sits on the line between the two kinds of price below.
Odds against and odds-on
When the first number is bigger than the second (5/2, 11/10, 7/4), the price is odds against: a winning bet makes more profit than the stake. The outcome is priced as less likely than not.
When the first number is smaller than the second (1/2, 4/6, 8/11), the price is odds-on: the profit is smaller than the stake, because the outcome is priced as more likely than not. Odds-on prices are often read the other way round, so 1/2 is "two to one on".
Worked example: 4/6
You stake 12 at 4/6.
- Profit: 12 × 4 ÷ 6 = 8
- Return: 8 + 12 = 20
You risk 12 to win 8.
From fractional odds to probability
A price also carries an implied probability: how often the outcome must happen for the price to break even. For a fractional price it is the second number divided by the sum of both numbers.
5/2: 2 ÷ (5 + 2) = 2 ÷ 7 ≈ 28.57%1/1: 1 ÷ 2 = 50%4/6: 6 ÷ (4 + 6) = 60%
The implied probability guide covers this in more depth, including why the probabilities across a whole market add up to more than 100%.
Converting to decimal and American odds
To decimal: divide the first number by the second and add 1. So 5/2 is 2.5 + 1 = 3.50, and 4/6 is 0.667 + 1 ≈ 1.67.
To American: if the price is evens or odds against, multiply the fraction by 100 and add a plus sign, so 5/2 is +250. If it is odds-on, divide 100 by the fraction and add a minus sign, so 1/2 is 100 ÷ 0.5 = -200.
From decimal back to fractional: subtract 1 and write the rest as a fraction. 2.75 minus 1 is 1.75, which is 7/4. Sportsbooks use a set ladder of traditional fractions, so a rounded decimal such as 1.91 is written as the nearest one, 10/11, rather than 91/100, and forms such as 4/6 and 6/4 are kept rather than reduced to 2/3 and 3/2.
| Fractional | Decimal | American | Implied probability |
|---|---|---|---|
| 1/2 | 1.50 | -200 | 66.67% |
| 4/6 | 1.67 | -150 | 60.00% |
| 10/11 | 1.91 | -110 | 52.38% |
| 1/1 (evens) | 2.00 | +100 | 50.00% |
| 11/10 | 2.10 | +110 | 47.62% |
| 7/4 | 2.75 | +175 | 36.36% |
| 5/2 | 3.50 | +250 | 28.57% |
| 10/3 | 4.33 | +333 | 23.08% |
Decimal, American and probability figures that do not divide exactly are rounded to two decimal places; the fractions are exact. You can convert any price with the converter:
Read as American odds: +150
+150 = 2.50 = 6/4 = 40.0%
The implied probability includes any margin in the price. A fair price comes from removing it.
Why fractions can be hard to compare
Fractions are easy to read on their own but awkward side by side. Does 13/8 pay more than 8/5? Converted, 13/8 is 2.625 and 8/5 is 2.60, so 13/8 pays slightly more, but that is hard to see from the fractions. Converting to decimal makes comparing prices a matter of picking the larger number.
No format shows the sportsbook's margin on its face. A two-way market at 10/11 on both sides looks balanced, yet each side implies 52.38%, so the pair adds up to 104.76%. The extra 4.76 percentage points is the overround, which works out to a margin of about 4.55% of all money staked; what the vig is explains both.
Betting carries a real risk of losing money; how to check a sportsbook licence shows how to confirm a sportsbook is licensed where you are, and if gambling stops feeling under control, free and confidential help is listed for every country at the end of that guide.