Convert character to decimal

I can’t seem to find a function to convert a character to a decimal.

Example:
Convert string ‘A’ into its decimal form ‘65’.

Background:
I’m trying to take an input character value (anything from a to ZZ), substring its characters, and into uppercase (eg. G, Z), covert each character to decimal (eg. 71, 90) and then reduce those numbers, such that A=0, B=1, Z = 25 and finally add them. GZ = 6+25 = 31.

It’s for an X,Y co-ord system that uses A-ZZ for X, and numbers for Y.