Odds, Probability & Bankroll
Fractional odds
Fractional odds are a betting format that shows the net profit you make on a winning bet relative to your stake, written as a/b or a-b.
Key points
- The fraction shows profit per unit staked: 7/1 wins 7 units for every 1 unit staked, plus the stake back 1.
- A losing bet returns nothing; the stake is forfeited 4.
- Common in UK and Ireland fixed-odds betting, especially horse racing 2.
Common questions
How do fractional odds work?
The fraction (a/b) tells you the net profit for each unit staked. For example, 4/1 means you win £4 for every £1 staked, and you get your stake back if you win.
How to read fractional odds?
Read the left number as profit and the right as stake. So 1/4 means you win £1 for every £4 staked — a short-priced favourite. 1/1 is even money.
Where this term is used
Related terms
Odds & probability
Fractional odds to decimal
Shows the formula and examples for converting fractional odds to decimal format.
Odds & probability
Odds
Explains the general concept of odds as a ratio of probability or a betting price.
Odds & probability
Betting odds
Covers the three main formats: fractional, decimal and American odds.
Odds & probability
Odds vs probability
Distinguishes between odds as a ratio and probability as a percentage chance.
Odds & probability
American odds
Describes the moneyline format used mainly in the US, with positive and negative numbers.
Odds & probability
Risk vs odds
Clarifies the difference between the amount risked and the odds offered.
Sources
- Odds en.wikipedia.org Provides the definition, alternative names, and examples of fractional odds.
- Fixed-odds betting en.wikipedia.org Confirms the use of fractional odds in UK and Ireland fixed-odds betting.
- Mathematics of bookmaking en.wikipedia.org Supplies the conversion formula to decimal odds and the mathematics of bookmaking.
- Sports betting - Wikipedia en.wikipedia.org Adds detail on how losing bets work and the prevalence in sports betting.
Sources are drawn from regulators, universities and published research, and each one is labelled with what it actually is — a preprint is not called a paper. Bookmaker and affiliate pages are never cited here, because a page that sells betting is not a neutral authority on it.