A 1 mm³ of blood contains 4 - 6 million of erythrocytes or red blood cells, 5 - 10 thousand leukocytes or white blood cells, and 150 - 400 thousand of platelets. Using the lower approximates of the cells to total number of cells will be 4.155 million cells in 1 cubic mm.
Percentage of red blood cells will be 4/ 4.155 = 96.27 %
Percentage of white blood cells =0.005/4.155 = 0.12 %
Percentage of the platelets = 0.15/4.155 = 3.61%