I would be using MD5 hashing to store encrypted passwords. Password can be 6 to 40 characters long. What is the database column size required for storing the encrypted password. Also, if 40 characters hash size is very large, then how much hash size would a 20 character password take?
I am using FormsAuthentication.HashPasswordForStoringInConfigFile(stringToEncrypt, "MD5"); to generate hash for storing in Database.
A hash algorithm always maps an arbitrary sized message to a fixed-length representation. In other words, you can hash an empty string or many gigabytes of information. The hash size is always fixed.
In your case the hash size is 128 bits. When converted to an ASCII string it would be a 32 character string that contains only hexadecimal digits.