Body surface area calculator
Enter your height and weight, get your BSA.
What is body surface area?
The total area of the skin, in square meters. Doctors use it to dose some drugs, such as chemotherapy, and to scale measurements like cardiac output.
How is BSA calculated?
The Mosteller formula is the simplest: √(height in cm × weight in kg ÷ 3600). 175 cm and 70 kg give 1.84 m².
Which formula should I use?
Mosteller (1987) is common for its simplicity; Du Bois (1916) is the oldest; Haycock (1978) was also fit on children. For typical adults they agree within a few hundredths of a square meter.
How much does BSA change with size?
Less than weight does, because it grows with the square root: 165 cm and 60 kg give 1.66 m², 175 cm and 70 kg give 1.84 m².
Can I use feet and pounds?
Yes — the calculator converts to centimeters and kilograms, which the formulas need.
How do the three formulas differ?
Mosteller is the square root of height (cm) times weight (kg) divided by 3,600. Du Bois is 0.007184 × weight^0.425 × height^0.725. Haycock is 0.024265 × weight^0.5378 × height^0.3964. Haycock’s 1978 paper measured the surface of 81 subjects from premature infants to adults and found that the Du Bois formula, then the most widely used, increasingly underestimated surface area below 0.7 m², by 7.96% in the newborn. In a 2022 comparison of nine formulas in 666 children aged 1 to 14 with hematological malignancies, Haycock had the smallest error (RMSE 0.009 m²) and Mosteller was close behind (0.012 m²). More than 40 formulas had been published by the end of the 20th century.
Worked example: an adult and a small child
For an adult of 175 cm and 70 kg, Mosteller gives √(175 × 70 ÷ 3600) = √3.403 = 1.84 m², Du Bois 1.85 m² and Haycock 1.85 m²: a spread of 0.003 m². For a child of 100 cm and 16 kg the formulas give 0.667 m² (Mosteller), 0.658 m² (Du Bois) and 0.669 m² (Haycock). The Du Bois value is the lowest, in line with Haycock’s finding for small bodies. If a treatment protocol is written in units per square meter, the amount is that figure times the BSA, so 50 units/m² would be 33.3 units for this child by Mosteller. Doses are set by the treating team, not by this arithmetic.
Common mistakes with body surface area
Entering inches where centimeters are expected: 70 inches typed as 70 cm, with 70 kg, returns 1.17 m² by Mosteller instead of 1.84 m² at 175 cm; keep the unit selector in step with the numbers. Mixing formulas: a protocol that names a formula should be followed with that formula, since the three can differ by hundredths of a square meter in adults and by several percent in newborns. Expecting precision for unusual body shapes: researchers who compared formulas with 3D scanning point out that the formulas are less accurate for people with unusual proportions. And confusing BSA with BMI: BSA is an area in m², BMI a ratio in kg/m².
Sources and related calculators
Sources: R. D. Mosteller, “Simplified calculation of body-surface area,” New England Journal of Medicine 317 (1987); D. Du Bois and E. F. Du Bois, Archives of Internal Medicine 17 (1916); G. B. Haycock, G. J. Schwartz and D. H. Wisotsky, “Geometric method for measuring body surface area,” Journal of Pediatrics 93 (1978); Q. Wu et al., “Evaluation of nine formulas for estimating the body surface area of children with hematological malignancies,” Frontiers in Pediatrics (2022); G. Redlarski et al., International Journal of Occupational Medicine and Environmental Health (2024). Related: BMI calculator, blood volume calculator, lean body mass calculator and creatinine clearance calculator.
For general information only — not medical advice. Talk with your doctor or another health professional about your own health. How we check our calculators.