Both formats tell you the same thing: how much you will be paid if your bet wins. The difference is in how the number is expressed.
Fractional odds are the traditional British format, still used by most high street bookmakers and on-course at racecourses. Decimal odds dominate online betting and are standard on exchanges. Knowing how to read both (and convert between them) takes about five minutes to learn.
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Fractional odds
Fractional odds are written as two numbers separated by a slash: 5/2, 4/1, 11/4, 1/2.
The number on the right is your stake. The number on the left is your profit if you win.
- 5/2: for every £2 staked, you profit £5. Total return: £7.
- 4/1: for every £1 staked, you profit £4. Total return: £5.
- 11/4: for every £4 staked, you profit £11. Total return: £15.
- 1/2: for every £2 staked, you profit £1. Total return: £3.
When the right-hand number is bigger than the left, you are looking at odds-on: the outcome is more likely than not according to the bookmaker.
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Decimal odds
Decimal odds are a single number representing your total return per £1 staked, including your stake.
- 5.00: stake £1, total return £5 (profit £4)
- 3.50: stake £1, total return £3.50 (profit £2.50)
- 1.50: stake £1, total return £1.50 (profit £0.50)
- 2.00: stake £1, total return £2 (profit £1, evens in fractional terms)
Anything below 2.00 in decimal is odds-on. Anything at 2.00 or above is even money or better.
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Converting between the two
Fractional to decimal: divide the left number by the right, then add 1.
5/2 = (5 ÷ 2) + 1 = 3.50
4/1 = (4 ÷ 1) + 1 = 5.00
1/2 = (1 ÷ 2) + 1 = 1.50
Decimal to fractional: subtract 1, then express as a fraction.
3.50 − 1 = 2.50 = 5/2
5.00 − 1 = 4.00 = 4/1
1.50 − 1 = 0.50 = 1/2
For common odds, bookmakers also have a standard name:
| Fractional | Decimal | Common name |
|---|---|---|
| 1/1 | 2.00 | Evens |
| 6/4 | 2.50 | Six-to-four |
| 2/1 | 3.00 | Two-to-one |
| 5/1 | 6.00 | Five-to-one |
| 10/1 | 11.00 | Ten-to-one |
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Why decimal is easier for analysis
For any kind of probability comparison or value calculation, decimal odds are simpler to work with.
Converting to implied probability: 1 ÷ decimal odds. No fractions required. See the implied probability guide for full detail.
Calculating expected value: (probability × decimal odds) − 1. Straightforward multiplication. See the expected value guide.
Comparing prices across bookmakers: decimal odds are directly comparable without conversion.
For this reason, most serious bettors and all modelling approaches, including BetSignals, use decimal odds internally.
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Setting your preferred format
Most online bookmakers let you switch between fractional and decimal in your account settings. If you are doing any kind of systematic analysis, set it to decimal and leave it there.
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Next reads
- How Football Odds Work: the broader picture of what odds represent
- Implied Probability Explained: using decimal odds to find the bookmaker's implied probability
- What is a Value Bet?: putting odds and probability together to identify edge
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