How do you convert fractional odds to decimal odds?

Divide the first number by the second, then add 1. For example, 5/1 becomes 5 ÷ 1 + 1 = 6.0, and 2/5 becomes 2 ÷ 5 + 1 = 1.40.

How do you calculate returns from decimal odds?

Multiply your stake by the decimal odds to get your total return, which already includes your original stake. A £10 bet at decimal odds of 6.0 returns £60 in total — £50 profit plus your £10 stake.

What does +500 mean in American odds?

A positive American odds figure shows the profit a £100 (or $100) stake would win. +500 means a £100 stake wins £500 profit, equivalent to fractional 5/1 or decimal 6.0.

What is implied probability in betting?

Implied probability is the chance of an outcome happening according to the odds on offer, calculated as 1 divided by the decimal odds. It includes the bookmaker's margin, so it tends to run slightly higher than the true underlying probability of the outcome.

Betting Odds Explained: Fractional, Decimal & American

Written by Andy Walker

Betting odds can be shown in three different formats — fractional (5/1), decimal (6.0), or American (+500) — and all three describe exactly the same thing: how much a bet could return and how likely the bookmaker thinks that outcome is. Once you know how to read one format, converting between them is straightforward. This guide walks through each format, shows how to calculate potential returns, and explains implied probability in plain terms.

Fractional odds are the traditional UK format, written as one number over another, such as 5/1 (read as "five to one"). The fraction tells you how much profit you'd win relative to your stake: a £10 bet at 5/1 wins £50 profit if successful, plus your original £10 stake back, for a total return of £60. With fractional odds where the first number is smaller than the second, such as 2/5, a £10 bet would win £4 profit (10 × 2/5), plus the £10 stake back, for a £14 return.

Decimal odds are more common across Europe and on betting exchanges, and are increasingly the default on many UK betting sites. A decimal price already includes your stake, so the calculation is simpler: return = stake × decimal odds. Odds of 6.0 are equivalent to fractional 5/1 — a £10 bet at 6.0 returns £60 in total (£10 × 6.0), which is the same £50 profit plus your £10 stake as the fractional example above. Decimal odds of 1.40 mean a £10 bet returns £14 in total.

American odds (also called moneyline odds) are the standard format in the US, shown as either a positive or negative number. A positive number, such as +500, shows how much profit a £100 stake would win — so +500 means a £100 bet wins £500 profit, equivalent to fractional 5/1 or decimal 6.0. A negative number, such as -200, shows how much you'd need to stake to win £100 profit — so -200 means a £200 bet is needed to win £100 profit, equivalent to fractional 1/2 or decimal 1.50.

All three formats can be converted into an implied probability — the chance of that outcome happening, according to the odds on offer. For decimal odds, the formula is implied probability = 1 ÷ decimal odds, expressed as a percentage. Odds of 6.0 imply a probability of 1 ÷ 6.0 = 16.7%. Odds of 1.50 imply a much higher probability of 1 ÷ 1.50 = 66.7%. For fractional odds, convert to decimal first by dividing the two numbers and adding 1 (5/1 becomes 5 ÷ 1 + 1 = 6.0), then apply the same formula.

It's worth remembering that implied probability from bookmaker odds includes a built-in margin (sometimes called the "overround"), meaning the probabilities across all outcomes in an event will typically add up to slightly more than 100%. That margin is how bookmakers generate revenue, so implied probability is a useful guide to how likely an outcome is considered, but it isn't a precise, unbiased measure of the true chance of it happening.

Understanding how to read and convert odds makes it easier to compare prices across different bookmakers and formats, and to work out realistic potential returns before you bet. As always, only stake what you can afford to lose, and if gambling stops feeling like entertainment, free and confidential support is available in the UK from BeGambleAware.org.

FAQs

How do you convert fractional odds to decimal odds?: Divide the first number by the second, then add 1. For example, 5/1 becomes 5 ÷ 1 + 1 = 6.0, and 2/5 becomes 2 ÷ 5 + 1 = 1.40.
How do you calculate returns from decimal odds?: Multiply your stake by the decimal odds to get your total return, which already includes your original stake. A £10 bet at decimal odds of 6.0 returns £60 in total — £50 profit plus your £10 stake.
What does +500 mean in American odds?: A positive American odds figure shows the profit a £100 (or $100) stake would win. +500 means a £100 stake wins £500 profit, equivalent to fractional 5/1 or decimal 6.0.
What is implied probability in betting?: Implied probability is the chance of an outcome happening according to the odds on offer, calculated as 1 divided by the decimal odds. It includes the bookmaker's margin, so it tends to run slightly higher than the true underlying probability of the outcome.