It depends on the SQL Server version.
http://technet.microsoft.com/en-us/library/ms143432.aspx
For SQL Server 2012, the batch size or SQL Statement (String) = 65,536 * Network packet size.
Network Packet Size is the size of the tabular data stream (TDS) packets used to communicate between applications and the relational Database Engine. The default packet size is 4 KB, and is controlled by the network packet size configuration option.
In short, 64K x 4K = 256 MB. Again, this assumes you are using default packet sizes.