The average adult human body contains about 4.5 to 5.7 liters of blood, which is roughly 7% to 8% of their body weight. This volume varies depending on factors such as age, sex, body size, and physiological conditions like pregnancy. For example:

• Adult males typically have around 5.5 liters of blood.
• Adult females generally have slightly less, about 4.3 to 4.5 liters.
• Pregnant women have 30% to 50% more blood volume to support fetal development.
• Children have about 8% to 9% of their body weight in blood.
• Infants have about 9% to 10% of their body weight in blood, approximately 75 to 100 milliliters per kilogram

In summary, an average adult human has about 5 liters of blood, but this can range from about 4.5 to 5.7 liters depending on individual factors.