Adults have about 70 mL of blood per kg (less in obesity). Estimating blood volume helps judge the significance of blood loss and plan transfusions and procedures such as apheresis.
How to use the Blood Volume Calculator
- Sex
- Height
- Weight
- Haematocrit
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter sex, height, weight and haematocrit.
Inputs explained
| Field | What to enter |
|---|---|
| Sex | Choose one: Male, Female |
| Height | Units: cm, in, m, ft, mm |
| Weight | Units: kg, lb, st, g |
| Haematocrit | In % |
What each result means
- Red cell volume = [Blood volume (Nadler)]×[Haematocrit]÷100
- Plasma volume = [Blood volume (Nadler)]×(1 – [Haematocrit]÷100)
Example values
How the main result changes when Height changes and everything else stays at the example values above:
| Height (cm) | Blood volume (Nadler) (L) |
|---|---|
| 87.5 | 3.26 |
| 131.25 | 3.85 |
| 175 | 4.98 |
| 218.75 | 6.86 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Nadler: men BV (L) = 0.3669 × H³ + 0.03219 × W + 0.6041
women BV (L) = 0.3561 × H³ + 0.03308 × W + 0.1833 (H in m, W in kg)
Red cell volume = BV × Hct · plasma volume = BV × (1 − Hct)
Worked example
Inputs — Sex: Male; Height: 175 cm; Weight: 75 kg; Haematocrit: 42 %.
Results — Blood volume (Nadler) = 4.98 L; Simple estimate = 5.63 L; Red cell volume = 2.09 L; Plasma volume = 2.89 L.
Key terms
- BV
- Blood volume.
Frequently asked questions
How much blood does an adult have?
About 4.5–5.5 litres, roughly 70 mL per kg.
How much blood can be lost safely?
Healthy adults tolerate about 15% loss (class I haemorrhage) without major symptoms.
Why does obesity change the estimate?
Fat has little blood supply, so mL/kg overestimates blood volume.