How this calculator works
Circulating blood volume per kilogram varies with age, prematurity and clinical condition. The presets explicitly select values within the ranges in the Iowa protocol table: preterm 100, term 85, infant 75 and child 70 mL/kg. These choices are the upper end for preterm neonates, midpoints for term neonates and infants, and the lower end for children. They are explicit conventions, not measured blood volume. Adolescent sex-specific factors are not inferred; use a clinician-selected coefficient when a different validated local convention is intended. This calculation does not set allowable blood loss or a transfusion trigger. The result is an estimate for information only and is not medical advice.
Formula
Estimated volume(mL) = body weight(kg) × selected coefficient(mL/kg). Weight(kg) = volume(mL)/coefficient(mL/kg).
Worked example
A 10 kg child at 70 mL/kg has an estimated 700 mL of circulating blood. A 3 kg term neonate at 85 mL/kg has an estimated 255 mL.
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Frequently asked questions
Why are different references different?
Blood volume is variable and reference tables often give ranges. This form displays the exact coefficient being used so the convention is visible.
Is the output a measurement?
No. It is a weight-based estimate. Acute illness and body composition can make the true volume different.
Can I infer safe blood loss from this?
No. Allowable loss and transfusion decisions also require haemoglobin, clinical condition and an individual treatment plan.