The average adult human body has about 5 liters of blood , which is approximately 7-8% of the total body weight. This amount varies depending on factors such as age, sex, body weight, and physiological conditions. For example, men typically have around 5.5 liters of blood, while women generally have slightly less, around 4.5 liters. During pregnancy, blood volume can increase by 30-50% to support fetal development. Children and infants have relatively higher percentages of blood volume relative to their body weight compared to adults.