Plasma Volume Calculator
The plasma volume calculator finds the blood plasma volume using the patient's hematocrit and weight. If you are curious about 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.
We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment.
What is the volume of plasma in a healthy person?
Plasma is a liquid that makes up around 55% of our blood volume. In preparation for the process of donating blood or in a laboratory blood test called hematocrit, blood plasma is 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 – including coagulation factors);
- Clotting factors (we refer to plasma as serum when it is without clotting factors);
- Electrolytes (Na+, Ca2+, Mg2+, HCO3−, Cl−, etc.);
- Hormones; and
- Carbon dioxide (plasma is the main medium of transportation of excretory products) and oxygen.
As plasma contains coagulation factors, some prone to bleeding patients will require plasma infusion. Find out more in our fresh frozen plasma dose calculator.
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 if you fill in the
Did you know that you can also calculate hemoglobin from hematocrit?
How do I calculate plasma volume from hematocrit 45% and weight 156 lbs for a woman?
The plasma volume for this woman is 2530 ml.
To calculate it step by step:
- Multiply the person's weight in kilograms by 70 ml (for males) or 65 ml (for females).
156 lbs = 70.8 kg
70.8 × 65 ml = 4602 ml
- Subtract the hematocrit value (as a fraction) from 1.
1 - 0.45 = 0.55
- Multiply the values from the equations above.
4602 ml × 0.55 = ~2530 ml
- You can double-check with our plasma volume calculator, too!
Does plasma have a definite volume?
No, plasma doesn't have a definite volume. However, we can roughly assess the plasma volume with the patient's weight and hematocrit. We can also estimate it from the patient's blood volume (plasma makes up ~55% of the blood volume).
How do I calculate blood plasma volume?
To calculate blood plasma volume, multiply total blood volume (TBV) by (1-Hct), where Hct (hematocrit) is a fraction.
PV = TBV × (1 - Hct)
There are three ways to calculate TBV where:
w means weight in kilograms, and
h is height in centimeters.
The simple method
TBV = 65 × wfor females
TBV = 70 × wfor males
TBV = (0.3669 × h^3 + 0.03219 × w + 0.6041)(males)
(0.3561 × h^3 + 0.03308 × w + 0.1833 )(females)
w × 70 / sqrt ( (w / h^2) /22 )(males)
w × 65 / sqrt ( (w / h^2) /22 )(females)
How do I increase blood plasma volume?
To get your body ready to donate plasma:
- Stay hydrated - drink 6-8 glasses of water (or other non-sugar beverages) daily.
- Eat a protein-rich, iron-rich meal before donating.
- Donate after a well-slept night.
- Avoid alcohol the day before.
- Avoid fatty foods before donation.