Fuzzy Match %age

Hi.

I have 3 numbers (lengths of String's if your interested)

8
14
6

8 is the length of String 1
14 is the length of String 2
6 is the number of characters that match between String 1 & 2.

Any idea how I work out the percentage of matching characters between
String 
1 & 2???

I want my function to return the matched characters (which it does) and a 
percentage matched.  e.g.  EFGHIJ - 84%


Cheers,
Steve.