BMI Calculator (Body Mass Index and BSA)

Calculate BMI and Body Surface Area

• BMI: This calculation is routinely used during clinical evaluations to estimate the appropriateness of an individual's weight relative to their height, serving as a preliminary step in identifying patients who are underweight or overweight.
• BSA: This formula estimates an individual's total external surface area, aiding in calculating dosages for medications, such as chemotherapy, and measuring cardiac index.

• Always use the most recent height and weight measurements to ensure accuracy.
• Remember that both BMI and BSA are part of a larger clinical context and should be used in conjunction with other assessments and patient history.

BMI:

• Does not distinguish between fat and muscle mass. 
• Tends to overestimate body fat in individuals with very high muscle mass who are otherwise healthy, and can underestimate it in older adults due to age-related muscle loss.
• The typical classification may underestimate the risk of cardiovascular disease associated with obesity in Asian populations. Organizations like the Wold Health Organization (WHO) and National Institutes of Health (NIH) recommend lower BMI thresholds for these individuals. Please see Evidence for more details.

BSA:

• Multiple formulas for BSA are available. This tool utilizes the Mosteller formula.
• May be less precise for neonates and infants, as well as for individuals at extreme values of height and weight.

BMI provides a quick estimate of adiposity, while BSA calculation helps estimate an individual's total external surface area, which is difficult to measure directly.