VERIFIED SOLUTION i

How to calculate the DAT file size of a MapInfo table

Product Feature: Data Creation/Import/Open
Product: MapInfo Pro, MapInfo Professional  
For the DAT file size calculation following column type sizes are relevant:
  • Character Field: 1 byte per character
  • Integer field: 4 bytes
  • Small Integer: 2 bytes
  • Large Integer: 8 bytes
  • Float field: 8 bytes
  • Decimal field: Decimal field width is the same as for character fields (1 byte per number or digit)
  • Date field: 4 bytes 
  • Time Field: 4 bytes 
  • Date/Time field: 8 bytes 
  • Logical Field: 2 bytes
The only difference with the field widths between old and extended TAB file format with respect to field widths is that for extended if the character set is UTF-16 the number of bytes for a character field is twice the field width. 
There are other differences between old and extended in that the DAT file headers are different sizes.
UPDATED:  September 11, 2017