Pediatric Blood Volume Calculator

Estimated blood volume is the approximate amount of blood circulating through a child's cardiovascular system. It is commonly expressed as milliliters per kilogram because body size changes dramatically from premature infancy through adolescence. This calculator multiplies body weight by a representative factor for the selected developmental group: 100 mL/kg for a premature infant, 85 mL/kg for a term newborn, 75 mL/kg for an infant, 70 mL/kg for a child, and 65 mL/kg for an adolescent. It displays the result in both milliliters and liters. The factors differ because blood volume represents a larger share of body weight early in life. A 3.5 kg term newborn, for example, has an estimated volume near 298 mL using 85 mL/kg. A 20 kg child has an estimate of 1,400 mL using 70 mL/kg. These values are useful for understanding scale and supporting clinical calculations, but the boundaries between age groups are not absolute. Local protocols may define infant, child, and adolescent groups differently or use a range rather than a single factor. Estimated circulating volume can inform assessment of blood loss, fluid resuscitation, extracorporeal circuit planning, phlebotomy limits, exchange procedures, and transfusion decisions. A percentage of blood loss can be clinically significant even when the absolute number of milliliters appears small. However, an estimate cannot determine current intravascular volume or prove hemorrhage. Hydration, edema, obesity, pregnancy, congenital heart disease, critical illness, burns, and other physiological states may change how body weight relates to circulating volume. Clinical teams interpret blood loss alongside heart rate, blood pressure, capillary refill, mental status, urine output, examination findings, serial laboratory results, and the circumstances of illness or injury. Emergency treatment should never wait for an online calculation when a child shows signs of shock or major bleeding. This calculator is intended for education and a quick arithmetic cross-check. It does not replace direct assessment, institution-specific guidance, or specialist judgment. Confirm the weight, choose the group deliberately, document assumptions, and use the resulting estimate only within a complete clinical evaluation.