This blood volume calculator estimates how much blood you carry — total volume, plasma and red-cell volumes — using the Nadler formula, the standard height-weight-sex estimation used across medicine.
Estimates for a typical adult body composition. The Nadler formula assumes standard proportions; obesity, bodybuilding, pregnancy and altitude adaptation move true volumes meaningfully (direct measurement uses tracer dilution). A standard blood donation removes about 500 mL — the card above shows your percentage.
The Nadler Formula
Men: BV = 0.3669 × H³ + 0.03219 × W + 0.6041 (liters, height in meters, weight in kg); women use 0.3561 / 0.03308 / 0.1833. The height-cubed term tracks frame volume; the rest calibrates against tracer-measured cohorts. Sanity band: roughly 65–75 mL/kg in adults — the per-kg card confirms your result sits in it. Blood is part of the fluid story our Total Body Water Calculator totals. Part of our Health Calculators collection.
Worked Example (Verified)
- Man, 175 cm, 70 kg (defaults): 0.3669 × 1.75³ (1.966) + 0.03219 × 70 (2.253) + 0.604 = 4.82 liters — 69 mL/kg, textbook center
- At hematocrit 45%: plasma 2.65 L, red cells 2.17 L — a donation of 500 mL takes ≈ 10.4% of the total, which the body replaces (fluid within a day or so, red cells over weeks, iron slowest)
- A 60 kg, 165 cm woman estimates ≈ 3.9 L — about 80% of the male example, scaling with frame as the formula intends
- Why endurance athletes run higher: training expands plasma volume 10–20% (the “sports anemia” dilution illusion in lab values) — estimation formulas describe the average, and athletes aren’t
Where Blood Volume Is Real Medicine
- Allowable blood loss & transfusion planning: surgical math starts from estimated volume and the patient’s hematocrit floor.
- Donation eligibility: minimum-weight rules exist so a fixed 500 mL draw stays a safe fraction of smaller donors’ volumes — the percentage card makes the rule tangible.
- Polycythemia and true anemia workups compare measured vs predicted volumes; pregnancy expands volume ~40–50% by term (an adaptation, not an error).
- Burn resuscitation formulas (Parkland) key off weight, not volume — different question, different tool.
Related Tools
- Total Body Water Calculator — the full fluid inventory
- Blood Pressure Calculator — the pressure in those vessels
- Health Calculators — the full collection
Frequently Asked Questions
How much blood does an average adult have?
About 4.5–5.5 liters for a typical man (the worked example: 4.82 L) and 4–5 liters for a typical woman — roughly 7% of body weight, or 65–75 mL per kilogram. Children run higher per kg (~80 mL/kg), infants higher still.
How is blood volume calculated?
Clinically by estimation formulas like Nadler’s (height³, weight and sex terms), validated against gold-standard tracer dilution studies. This calculator implements Nadler — the most widely used — and cross-checks against the mL/kg band.
What fraction of blood is plasma vs cells?
Your hematocrit decides: at the typical 45%, red cells are 45% of volume and plasma 55% (with a sliver of white cells and platelets — the buffy coat). The split cards here use your hematocrit input; 40–50% spans most healthy adults.
How much blood can you lose safely?
Donation’s 500 mL (~10%) is replaced fluid-wise within about a day. Clinical hemorrhage classes escalate from <15% (minimal symptoms) through 15–30% (tachycardia) to >40% (life-threatening) — those thresholds are exactly fractions of the volume this page estimates.
Does blood volume change with fitness or altitude?
Yes — endurance training expands plasma volume measurably within weeks, and altitude acclimatization increases red cell mass over months. Formula estimates assume sea-level, untrained averages, which is why measured volumes in athletes surprise on the high side.
Is this blood volume calculator free?
Yes — free, instant, no sign-up. An educational estimate, not a clinical measurement.