Row heights are measured in points or pixels.  There are 72 points to an inch
and "maybe" 96 pixels to the inch.

The number that appears in the Standard column width box is the average number
of digits 0-9 of the standard font that fit in a cell.

For an interesting and enlightening discussion on this subject see

http://snipurl.com/dzz8

If you want to use VBA to set height and width in mm which you can convert to
inches.

Ole Erlandson has code for setting row and column dimensions.

http://www.erlandsendata.no/english/index.php?d=envbawssetrowcol

Gord Dibben Excel MVP