Britannica Sources used in this answer

How much blood does an average adult human body contain?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Blood plasma — blood Blood sediment in test tubes, showing plasma (clear fluid), red blood cells (red), and the release of hemoglobin into the surrounding plasma (pink).

An average adult human body contains approximately 8 to 12 pints (about 4.5 to 6.8 liters) of blood, which accounts for roughly 7–8 percent of total body weight.1

While this is a general estimate, the specific volume of blood varies based on factors such as age, sex, weight, and body type. For instance, men typically have a larger blood volume than women due to differences in body size and composition. Additionally, blood volume can change significantly under certain conditions, such as during pregnancy, when it may increase by 25 to 50 percent to support the developing fetus.12

The body is highly efficient at maintaining a stable blood volume, balancing it with extravascular fluids even when water intake or loss fluctuates. Because the body maintains an adequate reserve, healthy individuals can generally tolerate the loss of about a pint of blood, such as during a blood donation, as the body rapidly works to restore plasma and red blood cells.12