How to convert decimal odds to fractional oddsAnd vice versa...
Everybody has their own preference as to whether they read the odds in fractional or decimal format. Bookmakers, from experience, tend to set up accounts to have fractional odds by default. It is usually straightforward to change these odds so that you can be sure of the odds you’re betting on… But if you are reading an article and it shows the format that you’re not used to – how do you convert it?
We got our resident numbers enthusiast to work out the formula and put it in simple(ish) terms.
If you don’t want to learn the method but just check a conversion instead, take a look at our odds conversion table.
Converting fractional odds to decimal odds
The most straightforward conversion is to convert fractional to decimal. The other way requires more multiplication, which you’ll see further down the page. Fractional to decimal only requires two steps – addition then division.
Odds conversion formula
The first number (numerator) should be added to the second number (denominator) and then divided by the denominator.
A few examples here…
9/4 in decimals would be worked out in the following way:
9 add 4 = 13
13 divided by 4 = 3.25
Therefore 9/4 = 3.25
7/2 in decimals would be worked out in the following way:
7 add 2 = 9
9 divided by 2 = 4.50
Therefore 7/2 = 4.50
4/9 in decimals would be worked out in the following way:
4 add 9 = 13
13 divided by 9 = 1.44
Therefore 4/9 = 1.44
Now for the harder conversion method. You may want a calculator for this one…
Converting decimal odds to fractional odds
This conversion requires a bit more mathematical prowess, but still doable without a calculator (sometimes).
It’s all about multiplying the decimal odds until you manage to get rid of both decimal places. We will reverse engineer the examples above to explain this fully.
We have already established that 9/4 fractional odds is 3.25 in decimal. To prove this, we would have to do the following sum, whilst remembering that we need to eliminate the decimal places.
3.25 – Decimal places exist. Therefore, we add 3.25 on again.
3.25 + 3.25 = 7.50 – Decimal places exist. Therefore, we add 3.25 on again.
3.25 + 3.25 + 3.25 = 9.75 – Decimal places exist. Therefore, we add 3.25 on again.
3.25 + 3.25 + 3.25 + 3.25 = 13.00 – Decimal places now gone! First part done.
Now that we have a number with no decimal places, we can work out the fraction. As you can see, we had to multiply 3.25 four times in order to eliminate the decimal places. So, we deduct four from thirteen – this being the sum of adding 3.25 together four times.
13 – 4 = 9
The fractional odds would then be the result of the sum directly above this sentence – 9 – over the number of times the decimal was multiplied – 4.
Ready to go again with another example?
We know that 7/2 is 4.50.
4.50 – Decimal places exist. Therefore, we add 4.50 on again.
4.50 + 4.50 = 9.00
We multiplied 4.50 two times to eliminate the decimal places. So, we deduct two from nine.
9 – 2 = 7
The answer from the sum above is seven, over the number of times the decimal was multiplied, two.
The higher the denominator (second number) the harder this method is.
Remember that 4/9 decimal that we worked out as 1.44? Let’s have a look…
1.44 – Decimals exist
1.44 + 1.44 = 2.88 – Decimals exist
1.44 + 1.44 + 1.44 = 4.32 – Decimals exist
1.44 + 1.44 + 1.44 + 1.44 = 5.76 – Decimals exist
1.44 + 1.44 + 1.44 + 1.44 + 1.44 = 7.20 – Decimals exist
1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 = 8.64 – Decimals exist
1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 = 10.08 – Decimals exist
1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 = 11.52 – Decimals exist
1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 + 1.44 = 12.96
Decimals exist here, but there’s something that is key. Whilst bookmakers will only display their decimal odds to two decimal places, they are calculated using far more.
If we were to be precise, we could say that 4/9 as decimal odds is actually 1.44444444444. When multiplying this by 9 (as we have done in the workings above) it equates to something along the lines of 12.99999999999996 which, by anyone’s standards, is close enough to round up to the nearest whole number.
Therefore, we will round our 12.96 up to 13 then apply the logic used in the previous sums.
Note that if your sum is within 0.05 of a round number (12.95 for example) then it is usually safe to assume that the underlying decimal places would have made up this different, so round up. This is what we have done with the 12.96 above.
We multiplied 1.44 nine times to eliminate the decimal places. So we deduct nine from thirteen.
13 – 9 = 4
The answer from the sum above is four, over the number of times the decimal was multiplied, nine.
We weren’t lying when we said that converting fractional to decimal is easier! 4/9 is one of the more complicated scenarios, but there you have it. You can now convert odds between fractional and decimal.
There are various betting calculators out there that will handle this conversion for you. At the time of writing this, we are currently building our own calculators that will convert these odds for you. Until then, though, if you want to see the most common odds, take a look at our odds conversion table.
If you have any queries about this article or questions about betting in general, please do get in touch with us on social media or by visiting our contact page.