Patient Total Blood Volume (mL) Male (0.006012 x H3)/(14.6 x W)+604 Female (0.005835 x H3)/(15 x W) +183 H=height in inches W=weight in pounds. But you can always try estimating as well. Estimation of Total Blood Volumes is based on Gilcher’s Rule of Five. Gilcher’s Rule of Fives Blood Volume (mL/kg of Body Weight) Patient Obese Thin Normal Muscular Male 60 65 70 75 Female 55 60 65 70 Infant/Child - - 80/70 - The reason for the difference is secondary to the difference in vascularity between adipose tissue and muscle tissue. For very obese patients you can estimate the total blood volume by using the lean body weight plus 20%. For Pediatric patients you can use. Pediatric Total Blood Volume Age Group Approximate Blood Volume (mL/kg) Premature infant at birth 90-105 Term newborn infant 80-90 Children (<3 months) 70-75 Adolescents Male 70 Female 65