The maximum number of columns you can create in a table is:
Fixed-length columns in allpages-locked and data-only-locked tables – 1024.
Variable-length columns in an allpages-locked table – 254.
Variable-length columns in a data-only-locked table – 1024.
The maximum size of a column depends on:
Whether the table includes variable- or fixed-length columns.
The logical page size of the database. For example, in a database with 2K logical pages, the maximum size of a column in an allpages-locked table can be as large as a single row, about 1962 bytes, less the row format overheads. Similarly, for a 4K page, the maximum size of a column in an allpages-locked table can be as large as 4010 bytes, less the row format overheads.