Set Excel 2013 cell size in millimeters (or inches for those relics living in US)
Open new excel sheet. Select desired paper size (A4 or A3... of course), orientation and set margins. Open View tab. Click Page Layout under Workbook Views. Press Ctrl+A. Open Home tab. Click Format under Cells. Select Row height and enter desired size with mm suffix (or "in" for rednecks) Click Format under Cells Select Column width and enter desired size. Open View tab. Click Normal under Workbook Views. Done.