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Body surface area (BSA) calculator
Body surface area in m² by the Mosteller formula is √(height in cm × weight in kg ÷ 3600). A child who is 100 cm tall and weighs 16 kg has a BSA of √(1600 ÷ 3600) = 0.67 m². This calculator also shows the Haycock and Du Bois results so you can see how closely they agree.
Source: N Engl J Med 1987;317(17):1098
Calculate BSA
The three formulas
| Formula | BSA (m²) | Published |
|---|---|---|
| Mosteller | √(height cm × weight kg ÷ 3600) | N Engl J Med 1987;317(17):1098 |
| Haycock | 0.024265 × height0.3964 × weight0.5378 | J Pediatr 1978;93(1):62-66 |
| Du Bois | 0.007184 × height0.725 × weight0.425 | Arch Intern Med 1916;17:863-871; Nutrition 1989;5:303-311 |
Where BSA is used
BSA scales some drug doses (especially chemotherapy), fluid requirements in burns, and normalizes kidney function (eGFR per 1.73 m²). For most everyday pediatric medicines, doses are weight-based instead: see the weight-based dose calculator.
Common questions
What is the Mosteller formula?
BSA (m²) = √(height in cm × weight in kg ÷ 3600). It was published in 1987 as a simpler alternative to older formulas and is widely used in pediatrics.
What is a normal BSA for a child?
It depends on size. By Mosteller, a 3.5 kg, 50 cm newborn is about 0.22 m², a 10 kg, 75 cm one-year-old about 0.46 m², and 1.73 m² is the conventional adult reference value.
Which BSA formula is most accurate for children?
Mosteller, Haycock and Du Bois usually agree closely. Haycock’s formula was validated in infants, children and adults; Du Bois dates from 1916 and was built from a small number of measured subjects. Many pediatric units use Mosteller because it’s easy to check by hand.
Sources
- Simplified calculation of body-surface area (Mosteller). N Engl J Med 1987;317(17):1098. Checked 2026-09-25.
- Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults (Haycock et al.). J Pediatr 1978;93(1):62-66. Checked 2026-09-25.
- A formula to estimate the approximate surface area if height and weight be known (Du Bois & Du Bois, 1916; reprinted 1989). Arch Intern Med 1916;17:863-871; Nutrition 1989;5:303-311. Checked 2026-09-25.