Blood Volume Calculator
An estimate of a person's total blood volume from height, weight and sex by the Nadler equations — with plasma and red cell volumes from the haematocrit, the volume per kilogram, and how much a unit of blood represents.
Blood volume tracks body size but not in proportion to weight, because fat carries little blood.
How the blood volume calculator works
Blood volume tracks body size but not in proportion to weight, because fat carries little blood. Nadler's 1962 equations use height cubed and weight with separate constants for men and women, and remain the standard estimate: about five litres for an average man, four for a woman, or roughly 65 to 75 millilitres per kilogram.
The haematocrit splits that into plasma and red cells, which is what transfusion, dialysis and pharmacokinetic dosing actually need.
Formula: men: BV = 0.3669 h³ + 0.03219 w + 0.6041; women: BV = 0.3561 h³ + 0.03308 w + 0.1833 (h in m, w in kg, BV in L)
Worked examples
| Inputs | Total blood volume (L) | Note |
|---|---|---|
| A 178 cm, 80 kg man | 5.249 | about 5.3 L |
| A 165 cm, 62 kg woman | 3.834 | about 3.8 L |
| A tall, lean man | 6.061 | more per kilogram |
FAQFrequently asked questions
How much blood does a person have?
About five litres for an average adult man and four for a woman — 65 to 75 millilitres per kilogram of lean body. Nadler's equations give a better estimate than weight alone.
Why height cubed?
Because blood volume scales with body volume, which scales with the cube of a linear dimension. The weight term adjusts for build.
What is the haematocrit?
The share of blood volume that is red cells — about 40 to 45% in men and 36 to 42% in women. The rest is plasma.
How much can be donated?
About 10% — 450 to 500 mL — every few months. The plasma is replaced within a day or two; the red cells take weeks.
Is this accurate in obesity?
Less so: fat tissue has a low blood supply, so per-kilogram estimates overshoot. Nadler partly corrects for this through the height term; ideal or adjusted body weight is sometimes used instead.
Where these figures come from
- NCBI Bookshelf — Molecular Biology of the Cell — growth kinetics and molecular conventions
- CSIRO — Australia's national science agency
Last checked: September 2026. Formulas are the standard textbook forms; assumptions are stated on each page because they are where these models break.