An average adult human body contains approximately 4.5 to 5.7 liters (about 1.2 to 1.5 gallons) of blood, which typically accounts for roughly 7–8% of total body weight. Blood volume varies by sex, weight, and age, with adult males generally having 5–6 liters and females about 4–5 liters. Blood Volume Breakdown Adults: ~4.5–5.7 liters (approx. 9–12 pints). Children: ~70–80 mL of blood per kilogram of body weight. Infants: A newborn has about 75–85 mL of blood per kilogram of body weight, usually totaling only a few cups. Pregnancy: Pregnant individuals have 30–50% more blood volume to support the baby. Key Facts on Blood Volume Blood Loss: Losing about 1 pint (roughly 500 mL) is generally safe, as in blood donation, but losing over 40% of blood volume is often life-threatening. Composition: Roughly 10% of an adult's body weight is blood. Factors: People at higher altitudes, who have less oxygen to breathe, often have higher blood volume. Regeneration: The body can quickly replace lost plasma in a few days, but red blood cells take weeks.