Plasma Volume Calculator

By Małgorzata Koperska, MD
Last updated: Jul 07, 2018

The plasma volume calculator finds the blood plasma volume using the patient's hematocrit (Hct) and weight. If you're curious what is the volume of plasma or how it's estimated, read on!

Please note that this is a calculator of blood plasma for adults. It doesn't estimate plasma volume for children.

What is the volume of plasma in a healthy person?

Plasma is a liquid that makes up around 55% of blood volume. In the preparation process of donated blood or in a laboratory blood test called hematocrit, it's separated by centrifugation from the formed elements of blood. They constitute the other 45%, most of which are red blood cells.

The components of blood plasma volume are:

  • water (up to 95% by volume);
  • dissolved proteins (6–8%) (serum albumins, globulins, and fibrinogen);
  • glucose;
  • clotting factors (plasma without clotting factors is called serum);
  • electrolytes (Na+, Ca2+, Mg2+, HCO3−, Cl−, etc.);
  • hormones,
  • carbon dioxide (plasma is the main medium of transportation of excretory products) and oxygen.

How does the blood plasma volume calculator work?

To calculate blood plasma volume (PV), you need the values of hematocrit (Hct) and total blood volume (TBV):

PV = TBV * (1-Hct)

The plasma volume calculation is usually performed on the assumption that the patient's total blood volume (TBV) is 70 mL per kg body weight for males and 65 mL per kg body weight for females. In our blood volume calculator, we use far more complicated methods of estimating TBV. You can calculate blood plasma volume more accurately using these methods in advanced mode.

Małgorzata Koperska, MD