does how much blood in the body vary by size
Scientists estimate the volume of blood in a human body to be approximately 7 percent of body weight. An average adult body with a weight of 150 to 180 pounds will contain approximately 4.7 to 5.5 liters (1.2 to 1.5 gallons) of blood. An average child with a body weight of 80 pounds will have approximately half the amount of blood as an adult. Blood carries out many critical functions in the body. It transports nutrients and oxygen to the body's cells.