What this calculator does
It estimates how much blood is in an adult's body from sex, height and weight, using Nadler's formula. That estimate is used in medicine, for example to plan for blood loss in surgery, and it's also handy for anyone curious about how much blood they have.
How it's calculated
Nadler, Hidalgo and Bloch (1962) fitted these equations to measured blood volumes in healthy adults. Height is in meters and weight in kilograms, and the answer is in liters:
Women: BV = 0.3561 × H³ + 0.03308 × W + 0.1833
US units are converted with 1 in = 2.54 cm and 1 lb = 0.45359237 kg. Calcist also shows the result per kilogram of body weight, and in US pints (1 pint = 0.473176 L).
Worked example
A man who is 1.78 m (5 ft 10 in) and weighs 77 kg (170 lb):
0.03219 × 77 = 2.479
2.069 + 2.479 + 0.6041 = 5.15 liters
That's about 5,150 mL, or 67 mL for each kilogram he weighs. A woman of the same height and weight comes out at about 4.74 liters, because her formula has smaller constants.
Sample results
| Height | Weight | Men | Women |
|---|---|---|---|
| 5 ft 4 in (163 cm) | 130 lb (59 kg) | 4.08 L | 3.66 L |
| 5 ft 7 in (170 cm) | 150 lb (68 kg) | 4.60 L | 4.19 L |
| 5 ft 10 in (178 cm) | 170 lb (77 kg) | 5.15 L | 4.74 L |
| 6 ft 1 in (185 cm) | 200 lb (91 kg) | 5.86 L | 5.45 L |
Each row uses the exact US height and weight. StatPearls notes that the average adult has nearly 5 liters of circulating blood, and that women tend to have less than men.
When the estimate doesn't apply
- Children. The formula comes from adults. Doctors use different estimates for children and babies.
- Pregnancy. Blood volume rises a lot during pregnancy (StatPearls gives roughly 50%), so the formula will be too low.
- Very high body weight. Fat holds less blood than lean tissue, so a weight-based formula can overestimate blood volume in people with obesity.
- Fitness, altitude and illness change blood volume, and none of them are in the formula.
Treat the answer as a population estimate. Measuring real blood volume takes a lab test.
Sources
- Nadler SB, Hidalgo JH, Bloch T. Prediction of blood volume in normal human adults. Surgery 1962;51(2):224–232.
- Sharma R, Sharma S. Physiology, Blood Volume. StatPearls (NCBI Bookshelf). — lists Nadler's equations and the average of nearly 5 liters.