Educational tool — not a treatment guide. Estimated blood volume supports clinical decisions such as transfusion and apheresis planning; it does not replace direct assessment of the patient by a qualified clinician.
Do not use this page to make treatment decisions. Estimates apply to adults and are not validated for children or pregnancy.
Quick answer: Nadler's equation estimates total blood volume from height, weight and sex. An average adult has about 5 litres, roughly 7–8% of body weight. Plasma volume is blood volume × (1 − haematocrit); red cell volume is blood volume × haematocrit.
Nadler's equation
Female: TBV (L) = 0.3561 × height(m)³ + 0.03308 × weight(kg) + 0.1833
Published by Nadler and colleagues in 1962, this remains the most widely used estimate of total blood volume in adults. It improves on the simple "7% of body weight" rule by accounting for height, since a tall lean person and a short heavy person of the same weight do not have the same blood volume.
Worked example — a 180 cm, 80 kg man (height 1.80 m):
- Height cubed: 1.80³ = 5.832
- 0.3669 × 5.832 = 2.140
- 0.03219 × 80 = 2.575
- Total: 2.140 + 2.575 + 0.6041 = 5.32 litres
Nadler SB, Hidalgo JU, Bloch T. Prediction of blood volume in normal human adults. Surgery, 1962;51:224–232.
Splitting blood into its parts
Plasma volume = TBV × (1 − haematocrit)
Haematocrit is the fraction of blood made up of red cells, typically about 0.40–0.54 in men and 0.36–0.48 in women. Enter it above and the calculator splits your total blood volume into red cell and plasma volumes — the figures used in transfusion and apheresis planning. With a haematocrit of 0.45, plasma is 55% of blood volume and red cells 45%.
Frequently asked questions
How is total blood volume calculated?
Nadler's equation estimates it from height, weight and sex. For men, TBV (litres) = 0.3669 × height(m)³ + 0.03219 × weight(kg) + 0.6041. For women, TBV = 0.3561 × height(m)³ + 0.03308 × weight(kg) + 0.1833. A 180 cm, 80 kg man is estimated at about 5.3 litres.
How much blood does the average person have?
Roughly 5 litres in an average adult, or about 7 to 8 percent of body weight. Men tend to have slightly more than women of the same size. Nadler's equation gives a more individualised estimate than the simple body-weight rule.
What is plasma volume?
Plasma is the liquid part of blood, the fraction that remains after the red cells are removed. Plasma volume = total blood volume × (1 − haematocrit). With a haematocrit of 0.45, plasma is 55 percent of blood volume, so a 5-litre blood volume contains about 2.75 litres of plasma.
What is red cell volume?
Red cell volume is the portion of blood made up of red blood cells: total blood volume × haematocrit. With a haematocrit of 0.45, a 5-litre blood volume has about 2.25 litres of red cells. It is used in transfusion and apheresis calculations.
Why does blood volume matter clinically?
Estimated blood volume is used to plan transfusion, estimate allowable blood loss during surgery, and prescribe apheresis and exchange procedures. It is an estimate that supports clinical judgement rather than replacing direct assessment of the patient.
References
- Nadler SB, Hidalgo JU, Bloch T. Prediction of blood volume in normal human adults. Surgery, 1962;51:224–232.
- Standard definitions of red cell volume and plasma volume in terms of total blood volume and haematocrit.