How much blood do you have?
Blood volume depends mainly on body size. Nadler’s formula, published in 1962 and still widely used, estimates it from sex, height and weight:
- Men: BV (L) = 0.3669 × height³ + 0.03219 × weight + 0.6041
- Women: BV (L) = 0.3561 × height³ + 0.03308 × weight + 0.1833
Height is in meters and weight in kilograms. Most adults have between 4.5 and 6 liters, roughly 70 mL per kg in men and 65 mL per kg in women.
Worked example
A man who is 5 ft 10 in (1.778 m) tall and weighs 180 lb (81.6 kg), with a hematocrit of 42%:
- Height cubed: 1.778³ = 5.62.
- Blood volume: 0.3669 × 5.62 + 0.03219 × 81.6 + 0.6041 = 5.29 L, about 11.2 pints.
- Per kilogram: about 65 mL/kg.
- Plasma volume: 5.29 × (1 − 0.42) = 3.07 L.
- Red cell volume: 5.29 × 0.42 = 2.22 L.
- A 1-pint donation is about 8.9% of his blood volume.
Blood components
| Component | Share of blood volume | Role |
|---|---|---|
| Plasma | about 55% | water, proteins, salts, nutrients |
| Red blood cells | about 40 to 45% (hematocrit) | carry oxygen |
| White cells and platelets | about 1% | immunity and clotting |
Why it matters
- Blood donation: donors in the US must weigh at least 110 lb, partly so that a 1-pint donation stays a small share of their blood volume.
- Surgery and trauma: doctors use blood volume to estimate how much loss a patient can tolerate.
- Medicine dosing and research: some drugs and dyes are dosed by blood or plasma volume.
Limits
Nadler’s formula was built from healthy adults. It is less accurate for people with obesity, athletes with high muscle mass, pregnant women, whose blood volume rises by 40 to 50%, and children, for whom pediatric values per kilogram are used instead.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.