How Many Pints of Blood Does a Human Have?

A typical adult human has approximately 8 to 12 pints (about 4.5 to 6.8 liters) of blood circulating through their body. This is equivalent to roughly 7–8 percent of total body weight.

Blood volume, however, varies according to factors such as age, sex, weight, and body type. In women, for example, blood volume is generally slightly less than that of men, owing to differences in body size and composition. However, during pregnancy, a woman’s blood volume increases significantly—from 25 to as much as 50 percent by the final stages of gestation—to support the growing fetus. This increase is due primarily to an augmented volume of blood plasma, the liquid component of blood.

The human body is adept at maintaining a stable blood volume. Even with fluctuations in water intake and loss, the body quickly balances the blood volume with extravascular fluids. The body also can tolerate a certain amount of blood loss without adverse effects. For example, donating a pint of blood is generally safe for healthy individuals, since the body rapidly replaces the lost plasma within hours and the red blood cells within several weeks.