How this calculator works
Plasma is the non-cellular fraction of blood. This estimate multiplies each adult blood-volume equation by one minus hematocrit expressed as a fraction. Nadler uses height and weight with separate historical male and female coefficient sets. Lemmens adjusts a 70 mL/kg reference by the square root of BMI divided by 22 and uses one equation for both sexes. The weight-only estimate uses an explicit editable coefficient. These are population equations, not direct volume measurements, and can differ substantially in obesity, pregnancy, critical illness or altered fluid balance. Inverse modes recover one input under a chosen equation; the coefficient-set selector applies only to Nadler inverse calculations. The result is an estimate for information only and is not medical advice.
Formula
Nadler blood volume (L): male = 0.3669 h³ + 0.03219 w + 0.6041; female = 0.3561 h³ + 0.03308 w + 0.1833. h in m, w in kg. Lemmens volume (mL) = 70 w / sqrt[(w/h²)/22]. Weight-only volume (mL) = coefficient x w. Plasma volume = blood volume x (1 - Hct fraction).
Worked example
At 1.8 m and 80 kg, Nadler gives blood volumes 5.3190608 L (male coefficients) and 4.9064752 L (female). At Hct 40%, plasma estimates are 3.19143648 L and 2.94388512 L.
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Frequently asked questions
Do these equations measure my actual volume?
No. They estimate a typical volume for body measurements; direct measurement requires a clinical method.
Why is there one Lemmens output?
The cited BMI-adjusted equation uses the same 70 mL/kg reference for both sexes. A second sex-specific coefficient is not invented.
Can I use these equations for children?
No. The displayed population equations are adult estimates; paediatric blood volumes need an age-appropriate method.