BSA Calculator (Body Surface Area)
This BSA calculator works out body surface area from height and weight using the Mosteller, Du Bois or Haycock formula. Example: 175 cm and 70 kg give 1.84 m² with Mosteller.
Example: Units: cm and kg · Height in cm 175 cm · Weight in kg 70 kg · Formula for the main result: Mosteller (1987) → Result: Body surface area (Mosteller) = 1.84 m². Source: Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098. Updated: .
How it is calculated
Body surface area (BSA) is the estimated area of the skin in square metres. It can hardly be measured directly, so it is calculated from height and weight. Medicine uses it as a reference quantity – for dosing chemotherapy, for the cardiac index or for normalising kidney function to 1.73 m².
The three formulas
Mosteller (1987): BSA = √(height in cm × weight in kg ÷ 3600). Du Bois and Du Bois (1916): BSA = 0.007184 × weight^0.425 × height^0.725. Haycock (1978): BSA = 0.024265 × weight^0.5378 × height^0.3964. Mosteller is the most widely used because it is so simple, Du Bois is the oldest and appears in many studies, and Haycock was validated in infants, children and adults.
Worked example
175 cm and 70 kg with Mosteller: 175 × 70 = 12250; divided by 3600 that is 3.4028; the square root is 1.8447 m², rounded to 1.84 m². Du Bois gives 1.8481 m² for the same person and Haycock 1.8468 m². For a child of 110 cm and 20 kg the values are 0.7817 (Mosteller), 0.7750 (Du Bois) and 0.7832 m² (Haycock).
- For adults of normal weight the formulas differ only in the second or third decimal place.
- Larger gaps appear in very small children and in marked obesity or underweight.
- Inches and pounds are converted at 2.54 cm per inch and 0.45359237 kg per pound.
Frequently asked questions
How do you calculate body surface area?
The simplest way is Mosteller: multiply height in cm by weight in kg, divide by 3600 and take the square root. For 175 cm and 70 kg that is 1.84 m².
Which BSA formula should I use?
It depends on the setting: hospitals and treatment protocols usually specify one. Mosteller is the most common; for children Haycock or Mosteller is often used.
What is body surface area used for?
As a reference quantity in medicine, for example for oncology dosing, the cardiac index or reporting kidney function per 1.73 m².
How much do the formulas differ?
In the example with 175 cm and 70 kg all three lie between 1.8447 and 1.8481 m² – a difference of less than 0.2 percent.
Sources and legal basis
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med 1916;17:863–871
- Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults. J Pediatr 1978;93:62–66
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