Decimal odds show the total return on £1 staked (2.50 → £2.50, £1 of it your stake). Fractional odds show the net profit (3/2 → £3 won on £2 staked). American odds show the profit on 100 staked (+150) or the stake needed to win 100 (−200). Odds of 2.50, 3/2 and +150 are one and the same price: an implied probability of 40%.
One price, three ways to write it
Decimal, fractional and American odds are three spellings of the same price. What changes is what the number counts: the total return, the net profit, or a reference stake of 100.
The implied probability doesn't depend on the format. Odds of 2.50 mean 40% whether you see 2.50, 3/2 or +150.
Decimal odds
Decimal odds show the total return for one unit staked, stake included. Most European bookmakers use them, UK sites offer them alongside fractional, and every calculator on this site works with them.
At 2.50, £1 staked returns £2.50. One pound is your stake coming back, so the net profit is £1.50. At 1.50, £1 returns £1.50, with £0.50 of profit.
That's what makes decimal easy to work with. Multiply the number by your stake and you're done. The implied probability takes one division, 1 ÷ odds, covered on implied probability.
Fractional odds
Fractional odds show the net profit, with the stake left out of the figure. Britain and Ireland have used them for a long time.
Odds of 3/2 pay 3 units for every 2 staked. On £10, that's £15 of profit and £25 back in total. The decimal equivalent is 3 ÷ 2 + 1 = 2.50.
The + 1 is the bit people forget. 1/1, known as "even money", is 2.00 in decimal and not 1.00, because the stake comes back on top of the profit.
American odds
American odds read differently depending on their sign, and the sign says nothing about winning or losing.
Positive odds show the net profit on 100 staked. +150 means 150 of profit on 100, which is 2.50 in decimal.
Negative odds show the stake needed to win 100 of net profit. −200 means staking 200 to win 100, which is 1.50 in decimal.
The dividing line is 2.00 in decimal, an implied probability of 50%. Above it the American price is positive, below it negative. Exactly 2.00 is written +100.
The equivalence table
Same prices, four units: decimal, fractional, American and implied probability. The table comes from the conversion engine behind the site's calculators, so the values match what the tools give you.
| Decimal | Fractional | American | Implied probability |
|---|---|---|---|
| 1.50 | 1/2 | −200 | 66.67% |
| 1.80 | 4/5 | −125 | 55.56% |
| 2.00 | 1/1 | +100 | 50.00% |
| 2.20 | 6/5 | +120 | 45.45% |
| 2.50 | 3/2 | +150 | 40.00% |
| 3.40 | 12/5 | +240 | 29.41% |
| 5.00 | 4/1 | +400 | 20.00% |
The last column is the one I'd read first. Row after row, the format on the left changes and the percentage on the right stays put.
Fractions are readable approximations. 4/5 is exactly 1.80, but not every decimal price lands on a tidy fraction. That's a limit of the format, not of the maths.
Convert odds into all four units →
Reading mistakes that keep coming back
Three confusions come up all the time, and two of them cost money.
- Mixing up profit and total return. Decimal odds of 3.00 return three times your stake in total, and one of those three is the stake itself. The profit is twice the stake. Fractional
2/1states that profit directly, which explains the apparent gap between the two. - Reading negative American odds as a loss.
−200is simply how a favourite is written. The larger the absolute value of negative odds, the likelier the price says the outcome is. - Thinking one format is better than another. No format gives bigger odds. A bookmaker showing
+150and one showing 2.50 offer the same price. To compare two bookmakers, convert to a common unit and strip out each margin, as explained on margin-free odds.
Quick check. A format tells you how a price is written and, once you know the convention, how much you'd win. It can't tell you whether the price is any good.
Put it into practice
Apply this guide to real odds.
See a market reading
A real match with its odds, movements and 0-100 signal.
Open the demoMargin calculator
Measure a bookmaker's margin on any market.
Calculate the marginDig into the market
Odds movements are only part of the story. Here are the next topics to read.
Odds and probability: the complete guide
The whole journey, from the displayed price to the closing line.
Read the guideImplied probability: how to get it from odds
The probability all three formats share, and what it doesn't tell you.
Convert oddsFair odds: from an estimated probability to a price
The calculation in reverse, in all three formats.
Work out fair oddsBookmaker margin: definition and calculation
What's inside a price, whichever format it's written in.
Understand the marginFrequently asked questions
Which odds format is traditional in the UK?
Fractional. It's the traditional format in Britain and Ireland, and it shows the net profit rather than the total return.
How do you read fractional odds?
Odds of 3/2 mean 3 units won for every 2 staked. That's 1.5 times your stake in profit and 2.5 times back in total.
What does −200 mean in American odds?
You stake 200 to win 100 in net profit. The minus sign marks a favourite, with decimal odds below 2.00. It says nothing about losing.
What does +150 mean in American odds?
A net profit of 150 on 100 staked. That's 2.50 in decimal and an implied probability of 40%.
Does the format change the implied probability?
No. The same price in decimal, fractional or American always gives the same implied probability and the same winnings.
How do I convert odds from one format to another?
OddScore's odds converter does all four conversions at once: decimal, fractional, American and implied probability. No account or sign-up needed.
Sources & methodology
This page draws on how odds are written in European and North American markets, the standard conversion formulas between formats, and OddScore's own odds-analysis method. The Gambling Commission and BeGambleAware are listed for the UK regulator's definitions and for player support.
- Convert each format to decimal odds, the pivot for every conversion.
- Work out the implied probability from the decimal odds (1 ÷ odds). It's the same whatever format you started from.
- Check every published equivalence against the conversion engine behind the site's calculators.
- Betfair: Exchange general rulessupport.betfair.com
- Betfair: Charges and commissionbetfair.com
- UK Gambling Commission: Definitions of terms
- BeGambleAware: support for players