Betting odds converter
How the conversion works
Fractional odds give the profit on your stake: 5/2 wins £5 for every £2 you bet. Decimal odds give the whole return, stake included, so a fraction converts by adding 1. 5/2 is 2.5, plus 1 makes 3.50. The chance a price implies is 100 divided by the decimal, so 3.50 is 28.57%.
Going the other way, take 1 off the decimal and write what's left as a fraction. Bookmakers quote fractions from a fixed list of prices, the bookmaker odds ladder, so a decimal or a chance that falls between two of them, such as 2.12 on an exchange, comes out as its exact fraction (28/25) with the nearest price a bookmaker would offer (11/10).
Odds explained
What do betting odds mean?
They tell you what a bet pays and how likely the price says it is. 5/2 wins £5 for every £2 you stake, 3.50 returns £3.50 for every £1, and both imply a 28.57% chance.
How do you convert fractional odds to decimal?
Divide the first number by the second and add 1. 7/2 is 3.5, plus 1 makes 4.50. The 1 is your stake coming back.
How do you convert decimal odds to fractional?
Take 1 off and write what is left as a fraction. 1.80 leaves 0.8, which is 4/5.
How do you turn odds into a percentage chance?
Divide 100 by the decimal price. 11/10 is 2.10, and 100 divided by 2.10 is 47.62%, so a side priced at 11/10 needs to win more than 47.62% of the time to be worth backing.
What odds match a percentage chance?
Divide 100 by the chance. A 47% chance is 100 divided by 47, or 2.13, which is closest to 11/10 on the bookmaker ladder.
What does evens mean?
A price of 1/1, or 2.00 in decimal, and a 50% chance. A £10 bet at evens wins £10, so you get £20 back.
What are odds-on prices?
Any price shorter than evens: a fraction with the smaller number first, a decimal under 2.00 or a chance above 50%. At 1/2, or 1.50, a £10 bet wins £5.
Why is 10/3 written as 100/30?
Bookmakers kept the old ladder's spellings. 100/30 is 10/3, or 4.33, and 85/40 sits between 2/1 and 9/4 at 3.13. Their odds-on mirrors are 3/10 (1.30) and 40/85 (1.47).
What is the bookmaker's margin?
Add up the chances implied by the price on every outcome. With both sides at 10/11 (1.91), each is 52.38%, so the book adds up to 104.76%. The 4.76% over 100 is the bookmaker's margin, also called the overround.
How do you work out returns from decimal odds?
Multiply your stake by the price. £10 at 3.50 returns £35: £25 profit and your £10 back.
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