How many red blood cells are in the human body?
Red blood cell
20–30 trillion
Adult humans have roughly 20–30 trillion red blood cells at any given time, constituting approximately 70% of all cells by number.[18] Women have about 4–5 million red blood cells per microliter (cubic millimeter) of blood and men about 5–6 million; people living at high altitudes with low oxygen tension will have more. Red blood cells are thus much more common than the other blood particles: there are about 4,000–11,000 white blood cells and about 150,000–400,000 platelets per microliter.