trying to create my own odds for horse racing

[themoo500]

Hi everyone,

I'm trying to create my own odds for horse racing strictly based off of a cominbation of RPR and OR ratings (sort of a combination of the two). I'm not great with maths unfortunately but i was wondering if anyone has a website or a bit of guide on how to do that (obviously I will manually adjust in head depending on certain criteria but i'm looking for a very simple base line as to what a horses odds shoud be just based off the ratings)?

Any help would be greatly appreciated. 

[MCLARKE]

Welcome @themoo500. Not really my area but there may be some on here who can help.