errr, do you mean going from UMS to raw marks, as in 16/20 or something?
if so then it's pretty impossible to help. raw marks are moderated up and down basewd on the subject, the specification and also based on the marks you recieved in other modules. it's not a simple scale up - i got 58/60 in raw marks in an english exam last year, but it came out as 90/90 in UMS. i'm not complaining about that but, as i'm sure you can see, there isn't really much of a link.