Blood Volume Calculator
Estimate your total blood volume from sex, height, and weight using the Nadler equation, the Lemmens-Bernstein-Brodsky BMI method, or a simple weight-based average. Add a hematocrit to split the total into red cell volume and plasma volume, and see results in litres, millilitres, and millilitres per kilogram.
Formula
Worked example
A 1.80 m, 80 kg male by Nadler: 0.3669 × 1.80³ + 0.03219 × 80 + 0.6041 = 2.14 + 2.58 + 0.60 ≈ 5.32 L (about 5,320 mL, near 67 mL/kg). At a hematocrit of 45%, that is roughly 2,395 mL of red cells and 2,925 mL of plasma.
Three ways to estimate blood volume
Total blood volume is hard to measure directly, so clinicians estimate it from body size. The Nadler equation (1962) is the most widely used: it predicts blood volume in litres from height and weight with sex-specific coefficients, cubing height because volume scales with the cube of a linear dimension. The Lemmens-Bernstein-Brodsky equation (2006) instead works from body mass index, which makes it more reliable for people with obesity where the height-cubed term can overshoot. The simple weight-based method multiplies body weight by an average blood volume per kilogram and is the standard approach for children and neonates, who carry proportionally more blood than adults. This calculator offers all three so you can match the method to the situation.
Red cell volume and plasma volume
Blood is a mix of cells and fluid. Hematocrit is the fraction of blood volume taken up by red cells, typically 41 to 50 percent in men and 36 to 44 percent in women. If you enter a hematocrit, the calculator splits the total into red blood cell volume (total volume times hematocrit) and plasma volume (the remainder). These figures matter for exchange transfusion, apheresis, and estimating red-cell loss during surgery. Plasma volume in particular is used when calculating how much fluid or plasma to replace, while red cell volume guides decisions about packed-cell transfusion.
What blood volume means and why it matters
Blood volume is the total amount of blood circulating in the cardiovascular system, red cells, white cells, platelets, and plasma combined. A typical adult holds about 7 to 8 percent of their body weight as blood, roughly 4.5 to 5.5 litres, or near 70 millilitres per kilogram. Knowing this figure helps in transfusion medicine, estimating allowable blood loss during surgery, calculating exchange volumes for plasmapheresis, and weight-based drug dosing. A larger or smaller body, pregnancy, endurance training, and living at high altitude can all shift the real value away from the estimate.
Limits of the estimate
Each method was derived from a limited study population and assumes an average body composition. Nadler can over- or under-estimate volume for people who are very muscular, who carry significant excess fat, who are children, or who are pregnant; Lemmens is better for obesity but less validated at the extremes; the weight-based averages are approximations. Results from this calculator are estimates for general information only and are not a substitute for measurement or medical judgment. Any clinical decision, transfusion, surgery, or dosing, must be made by a qualified healthcare professional using validated tools and direct assessment.
Average blood volume by group
| Group | Per body weight | Typical total |
|---|---|---|
| Adult male | ~75 mL/kg | 5.0-6.0 L |
| Adult female | ~65 mL/kg | 4.0-5.0 L |
| Child (over 1 yr) | ~80 mL/kg | 2.0-2.5 L |
| Infant (1-12 mo) | ~80 mL/kg | 0.5-0.8 L |
| Term neonate | ~85 mL/kg | 0.25-0.30 L |
| Preterm neonate | ~100 mL/kg | 0.10-0.20 L |
Approximate average total blood volume per kilogram, used by the weight-based method. Adults hold roughly 7-8% of body weight as blood.
Frequently asked questions
How much blood is in the human body?
A typical adult has roughly 4.5 to 5.5 litres of blood, about 7 to 8 percent of body weight. Larger and taller people have more. The Nadler equation tailors the estimate to your sex, height, and weight, while children and neonates carry more per kilogram (around 80 to 100 mL/kg).
Which method should I use, Nadler or Lemmens?
Nadler is the long-standing clinical standard and works well for average adults. The Lemmens-Bernstein-Brodsky equation uses body mass index and is generally more accurate for people with obesity, where Nadler can over-estimate. For children and neonates, use the weight-based method with the matching age group.
How do I get red cell volume and plasma volume?
Turn on the hematocrit split and enter your hematocrit (the percentage of blood that is red cells). The calculator multiplies total blood volume by the hematocrit to get red cell volume, and the rest is plasma volume. Typical hematocrit is 41 to 50 percent in men and 36 to 44 percent in women.
Why does the Nadler formula use height cubed?
Volume scales with the cube of a linear measurement. Cubing height captures how overall body size grows in three dimensions, which is why height is the strongest driver of blood volume in the Nadler equation.
Is this calculator accurate enough for medical use?
It gives a reasonable population estimate, but it is for general information only. Clinical decisions about transfusion, blood loss, or dosing require direct measurement and a qualified healthcare professional.