Approximately how many liters of blood are in an average adult human?

Approximately how many liters of blood are in an average adult human?

• A. 4.0 liters
• B. 5.6 liters
• C. 7.5 liters
• D. 3.0 liters

Answer: (B)

Blood volume is about 7–8% of a person’s body weight. For a typical adult around 70 kg, that works out to roughly 5–6 liters of blood. Using the common estimate of about 0.08 of body weight gives 0.08 × 70 ≈ 5.6 liters, which fits well with everyday teaching that an average adult has about five liters of blood, with some variation. So 5.6 liters is a sensible approximate value for a standard adult. The smaller amounts would reflect smaller individuals or lower percentages, while a much larger amount like 7.5 liters would be unusually high for the average adult.

Blood volume is about 7–8% of a person’s body weight. For a typical adult around 70 kg, that works out to roughly 5–6 liters of blood. Using the common estimate of about 0.08 of body weight gives 0.08 × 70 ≈ 5.6 liters, which fits well with everyday teaching that an average adult has about five liters of blood, with some variation. So 5.6 liters is a sensible approximate value for a standard adult. The smaller amounts would reflect smaller individuals or lower percentages, while a much larger amount like 7.5 liters would be unusually high for the average adult.