I have a 3-9/16" thick door with the lock centered in the door as seen here:
View Image
Assuming the lock is centered in the door:
(DT-G+C1+C2)÷2
Example:
(3.5625-.25+.125+.125)/2 = 1.78125
Therefore you would be using 1-3/4" length cylinders (rounding for the 1/32")