How to read betting odds
A plain-English primer on Decimal, Fractional, and American odds — with conversion examples and a quick way to spot value.
Odds tell you two things at once: how much you stand to win, and how likely the bookmaker thinks an outcome is. The number is the same, only the format changes.
The three formats
Decimal (European)
Multiply your stake by the decimal price to see your total payout, including the stake. £10 at 2.50 returns £25 (£15 profit).
Fractional (UK)
The numerator is the profit per the denominator staked. 5/2 means £5 profit for every £2 staked. To convert to decimal: (numerator / denominator) + 1. So 5/2 = 3.50.
American
Positive numbers (e.g. +150) show the profit on a £100 stake. Negative numbers (e.g. −200) show the stake required to win £100. +150 = 2.50 decimal; −200 = 1.50 decimal.
Implied probability
Divide 1 by the decimal odds and multiply by 100. A price of 2.50 implies a 40% chance. If you reckon the true chance is higher than that, you have a value bet.
Add up the implied probabilities of every outcome in a market and the total comes to more than 100%. The extra is the bookmaker's margin, known as the overround: what the overround means for your bets.