# Calculation Engine - Formula Function Reference

## Frequently asked questions

The up-to-date F.A.Q. page for PhpSpreadsheet can be found on [http://www.codeplex.com/PHPExcel/Wiki/View.aspx?title=FAQ&referringTitle=Requirements][1].

### Formulas don’t seem to be calculated in Excel2003 using compatibility pack?

This is normal behaviour of the compatibility pack, Xlsx displays this correctly. Use \PhpOffice\PhpSpreadsheet\Writer\Xls if you really need calculated values, or force recalculation in Excel2003.

  [1]: http://www.codeplex.com/PHPExcel/Wiki/View.aspx?title=FAQ&referringTitle=Requirements