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Fractional Odds
Last reviewed 24 September 2026
What is Fractional Odds?
The traditional British odds format, expressing profit relative to stake. Odds of 5/1 return five units of profit for every one staked, plus the stake back.
Key takeaways
- Fractional odds express profit relative to stake: 5/1 pays five units of profit per unit staked, plus the stake back.
- Decimal odds equal the fraction plus one, so 5/1 is 6.00 and 6/4 is 2.50.
- Implied probability is the denominator divided by the sum of both numbers, so 6/4 implies a 40% chance.
Why it matters
Fractional odds are the historic format of British and Irish bookmaking and still dominate UK retail betting shops and horse racing. The left number is the profit, the right the stake: 5/1 pays five to one, while 1/2 (an odds-on price) pays half a unit of profit per unit staked. Prices such as 11/8 or 6/4 persist because they map to the fractions traditionally chalked on boards, which is also why the format is harder to compare quickly than decimals.
Converting is straightforward once the relationship is clear: decimal odds equal the fraction plus one, so 5/1 is 6.00 and 6/4 is 2.50. Implied probability is the denominator divided by the sum of both numbers, so 6/4 implies 40%. Most UK-facing operators now let customers switch between fractional and decimal display, a small but telling sign of how the audience has changed: the traditional racing customer reads fractions, while the modern multi-market bettor reads decimals.
Frequently asked questions
What are fractional odds?
Fractional odds are the traditional British and Irish way of quoting a price. The left number is the profit and the right number is the stake, so 5/1 returns five units of profit for every unit staked, plus the stake back. Odds-on prices such as 1/2 pay less than the stake in profit. The format still dominates UK betting shops and horse racing.
How do you convert fractional odds to decimal odds?
Divide the left number by the right number and add one. 5/1 becomes 6.00, 6/4 becomes 2.50 and 1/2 becomes 1.50. The decimal figure includes the returned stake, which is why it is always one higher than the fraction. Most UK-facing operators let customers switch between the two displays, so the conversion is usually done for them.
How do you work out implied probability from fractional odds?
Divide the right number by the sum of both numbers. For 6/4 that is 4 divided by 10, which implies a 40% chance; for 5/1 it is 1 divided by 6, or about 16.7%. The result includes the bookmaker's margin, so the implied probabilities of every outcome in a market add up to more than 100%.