Converting ratings into percentages

[wb]

I know this has come up before but I can’t find it.

Converting ratings into odds.

I’m working on odds compiling, and once all of my variables have been considered, the horse is given a rating, which reflects what I think its chances of winning are. I want to convert these figures into odds and wonder if there is a formula, or quick way of doing it in excel.

To give a simple example of what I’m talking about:

Horse A has a rating of 50
Horse B has a rating of 30
Horse C has a rating of 20

Total ratings added together: 100

Therefore Horse A has a 2.0 chance in decimal odds(100/50), Horse B has a 3.33 chance (100/30) and Horse C has a 5.0 chance (100/20)



Is this correct?

Ok, that’s an easy example as they all add up to 100, so what about odd figures…

Lets say the figures read:
Horse A: 235
Horse B: 220
Horse C: 175

Total ratings added together: 630.

Therefore, a 1% chance equals 6.3.

So…
Horse A would have a 2.69 chance (expressed in decimal odds) of winning right?
(235 divided by 6.3 equals 37.3 … then… 100 divided by 37.3 equals 2.69)



I know it’s pretty simple, but I just can’t remember how to convert. Am I on the right track, and are there any simple excel shortcuts I should know about?

Thanks

[mathare]

All you need to do is divide each rating by the sum of the ratings to get a percentage chance of winning, and divide the sum of the ratings by the individual rating to get the decimal odds equivalent.

So 235 / 630 = 0.3730.. ie 37.30% chance of winning
And 630 / 235 = 2.6808... ie decimal odds of 2.69

If you have this in Excel then use something along the lines of:

= A1 / SUM (A1:A8)

where A1 is the rating for Horse A and there are 8 horses in the race (in rows 1 to 8)

[wb]

Thanks Mat, I was over-complicating things a bit there!