The full grid on a hemocytometer contains 9 squares, each of which is 1 micro meter (mm) square.  Large cells are counted using the four large corner squares (and the middle one).

For a dense suspension of small calls, the four 1/25 sq. mm corners plus the middle square and the central square are used.

It consists of 9 large squares, each measuring 1 x 1 mm, with the depth of chamber of 0.1 mm.  Each square has a total volume of 0.1 mm³ or 10^-4cm³.  The central square is divided into 25 small squares with triple lines and four corner squares divided into 16 small squares.

Each large square has a surface area of 1.0mm², and a chamber depth of 0.1mm.  There are 1000 mm³ per ml, each large square represents a volume of 0.0001ml, that equates to 1/ 0.0001ml = 10,000 = (10⁴).  The volume factor is 10,000.

Cells per ml = Average count per square x dilution factor x 10,000