- Maths reviewed by Josh Miller
- Tested by Diana Westfield
A fractional to decimal odds conversion goes like this: divide the top by the bottom, then add 1. So 5/2 is 2.5, plus 1, which gives 3.50. Type any fraction into the free CasinoCalcs converter and it does it for you, along with the implied chance and what a bet pays back.
Fractional to decimal odds, the quick way
The added 1 is the stake. A 5/2 winner pays £5 profit for every £2, and you get the £2 back as well. Decimal odds fold that in: £2 × 3.50 = £7 back, £5 of it profit. Same bet, same money.
Odds-on prices work the same. 4/6 is 0.667, add 1, 1.67. 2/7 is 0.286, so 1.29. If the top number is smaller than the bottom, the decimal is under 2.
Awkward fractions in your head
Eighths are where people stall. 13/8? Think of it as one and five eighths. Five eighths is 0.625, so 1.625, plus 1 is 2.625. 15/8 is 2.875, 11/8 is 2.375. Learn 1/8 = 0.125 and you can do the lot.
Thirds and sixths come up less, but 10/3 (4.33) and 5/6 (1.83) both turn up on football and racing coupons.
Fractional to decimal odds chart
| Fractional | Decimal | £10 returns |
|---|---|---|
| 1/5 | 1.20 | £12.00 |
| 2/7 | 1.286 | £12.86 |
| 1/3 | 1.333 | £13.33 |
| 2/5 | 1.40 | £14.00 |
| 1/2 | 1.50 | £15.00 |
| 4/7 | 1.571 | £15.71 |
| 8/13 | 1.615 | £16.15 |
| 4/6 | 1.667 | £16.67 |
| 4/5 | 1.80 | £18.00 |
| 10/11 | 1.909 | £19.09 |
| evens (1/1) | 2.00 | £20.00 |
| 11/10 | 2.10 | £21.00 |
| 6/5 | 2.20 | £22.00 |
| 5/4 | 2.25 | £22.50 |
| 11/8 | 2.375 | £23.75 |
| 6/4 | 2.50 | £25.00 |
| 13/8 | 2.625 | £26.25 |
| 7/4 | 2.75 | £27.50 |
| 15/8 | 2.875 | £28.75 |
| 2/1 | 3.00 | £30.00 |
| 9/4 | 3.25 | £32.50 |
| 5/2 | 3.50 | £35.00 |
| 11/4 | 3.75 | £37.50 |
| 3/1 | 4.00 | £40.00 |
| 10/3 | 4.333 | £43.33 |
| 7/2 | 4.50 | £45.00 |
| 4/1 | 5.00 | £50.00 |
| 9/2 | 5.50 | £55.00 |
| 5/1 | 6.00 | £60.00 |
| 6/1 | 7.00 | £70.00 |
| 8/1 | 9.00 | £90.00 |
| 10/1 | 11.00 | £110.00 |
| 12/1 | 13.00 | £130.00 |
| 16/1 | 17.00 | £170.00 |
| 20/1 | 21.00 | £210.00 |
| 25/1 | 26.00 | £260.00 |
| 33/1 | 34.00 | £340.00 |
| 50/1 | 51.00 | £510.00 |
| 100/1 | 101.00 | £1010.00 |
Sites round the three-decimal ones differently. 13/8 can show as 2.62 or 2.63, 15/8 as 2.87 or 2.88. It’s the same price either way.
Why bother with decimals?
Because the maths gets easier the moment there’s more than one bet. Doubles, trebles and accas are just the decimals multiplied: 5/2 and 6/4 is 3.50 × 2.50 = 8.75, so £10 returns £87.50. Try that with fractions. The acca calculator chains as many as you like, and the decimal to fractional converter takes you back again.
A clear price makes it easier to stick to a budget, too. BeGambleAware.org can help if it’s getting hard to stop.