How many gallons of blood does the average human body have circulating through it?

The total amount of blood in a human can vary with age, sex, health condition, and body type. According to some studies, 7% of your body weight is made up of blood. A human between 150 and 180 pounds has between 4.5 and 5.5 liters, or 1.2 to 1.5 gallons.