Estimate total blood volume by age and weight.
Premature neonates: ~90 mL/kg. Term neonates: ~80 mL/kg. Infants: ~80 mL/kg. Children: ~75 mL/kg. Adults: ~70 mL/kg. These estimates guide maximum allowable blood loss calculations, transfusion volumes, and fluid resuscitation in pediatric patients. Actual volumes vary with gestational age and body composition.