Maximum characters of varchar max in sql server

Maximum 2^31-1 byte (2GB).

[2,147,483,647] Character

1 character = 1 byte

Variable-length, non-Unicode string data. n defines the string length and can be a value from 1 through 8,000. max indicates that the maximum storage size is 2^31-1 bytes (2 GB). The storage size, in bytes, is the value of the actual data entered + 2 bytes. The ISO synonyms for varchar are char varying or character varying.

Ref:

http://msdn.microsoft.com/en-us/library/ms176089(v=sql.105).aspx