Is there like a chart somewhere that shows how long a string becomes after performing md5() on it, based on the length of the original string?

Check the manual

Return Values

Returns the hash as a 32-character hexadecimal number.

I'm sorry, didn't see that when I checked the manual. So the length will always be 32 characters?

Yes, it will always be 32 characters in length.

So would a user registration form that had it's password input maxlength property set to 20, and the password field in the MySQL table set to varchar with a length of 32 work?

Sorry about all the questions. I messed up my login script tonight, and it took me awhile to figure out it was because I had changed the password length in the database.

So would a user registration form that had it's password input maxlength property set to 20, and the password field in the MySQL table set to varchar with a length of 32 work? Yes, the output character length is independent of the input character length.

Thanks!