The packed cell volume can be determined by centrifuging the blood in a capillary tube (a.k.a. a hematocrit tube), which forces the cells to one end. The length of the tube containing blood cells, divided by the length containing cells or plasma gives the PCV.

While usually used synonymously, the hematocrit is a value that is calculated by an automated analyser, and not directly measured. It is determined by multiplying the red cell count by the mean cell volume. The hematocrit is slightly more accurate as the PCV includes small amounts of plasma trapped between the red cells.