What are fractional odds?
Fractional odds are the traditional British format, written like 5/2, where the first number is the profit you win for staking the second number, with your stake returned on top.
Read the slash as “to”. 5/2 is “five to two”: win £5 for every £2 you stake. Your stake comes back as well, so the fraction only ever describes the profit.
This is the home format of UK and Irish bookies and of horse racing everywhere. US outlets use it for futures now and then (“the Lakers are 8/1”), but day-to-day American betting runs on plus and minus numbers. The rest of the world mostly uses decimals.
Example
You stake £10 at 5/2.
- Profit: 10 × 5 ÷ 2 = £25
- Total back: £25 + your £10 stake = £35
To convert to decimal, divide the fraction and add 1: 5 ÷ 2 + 1 = 3.50. For the implied probability, divide the right-hand number by the sum of both: 2 ÷ (5 + 2) = 28.6%.
| Fractional | Spoken as | Decimal | Profit on £10 |
|---|---|---|---|
| 1/2 | “two to one on” | 1.50 | £5 |
| 1/1 | “evens” | 2.00 | £10 |
| 6/4 | “six to four” | 2.50 | £15 |
| 5/2 | “five to two” | 3.50 | £25 |
| 10/1 | “ten to one” | 11.00 | £100 |
Watch out
- When the right-hand number is bigger (1/2, 4/6), the price is odds-on: you win less than you stake.
- Some traditional fractions are awkward. 11/8, 13/8 and 100/30 are hard to compare in your head. Quick: is 11/8 bigger than 6/4? (No. It’s 2.375 against 2.50.)
- That’s the real weakness of the format. Comparing prices across bookies is slow, and slow comparisons cost you value.
I switch every site to decimal for that reason. The odds converter handles any fraction.