Body Surface Area (BSA) Calculator – Mosteller, Du Bois
Calculates body surface area (BSA, m²) from height and weight with the Mosteller, Du Bois and Haycock formulas and shows all three side by side.
Things to keep in mind:
- Results are estimates and must not be used alone to calculate drug doses; doses are always set by a physician or pharmacist.
- In severe obesity, amputation, oedema or very low body weight the formulas can deviate noticeably from the real surface area.
- For infants and small children the Haycock formula is generally preferred; paediatric dosing follows the institution's protocol.
Calculator
Result
Enter the values and press Calculate to see the result here.
About this tool
Body surface area (BSA) estimates the total area of a person's skin in square metres. In medicine it is considered a better measure of body size than weight alone: some drug doses (especially chemotherapy), the cardiac index and the standardisation of kidney function to 1.73 m² are based on BSA. Because it is hard to measure directly, it is estimated from height and weight.
Formulas
With height (H) in centimetres and weight (W) in kilograms:
- Mosteller (1987): BSA = √(H × W ÷ 3600)
- Du Bois & Du Bois (1916): BSA = 0.007184 × W^0.425 × H^0.725
- Haycock (1978): BSA = 0.024265 × W^0.5378 × H^0.3964
The Mosteller formula is the most widely used in clinical practice because it is simple. Du Bois is the historical reference and Haycock was developed for children and infants. Results are rounded to 2 decimals.
Example
Height 170 cm, weight 70 kg:
- Mosteller: √(170 × 70 ÷ 3600) = √3.3056 = 1.82 m²
- Du Bois: 0.007184 × 70^0.425 × 170^0.725 = 1.81 m²
- Haycock: 1.83 m²
How to read the result
Adult men typically have a BSA around 1.9 m² and adult women around 1.6 m²; 1.73 m² is the "standard adult" value used in laboratory reports. In average adults the formulas usually differ by 0.02–0.05 m²; the gap grows for very heavy, very light or very short people. Which formula applies to a treatment is decided by the physician and the institution's protocol.
How to use
- Enter your height in centimetres (e.g. 172).
- Enter your weight in kilograms; decimals are allowed (e.g. 68.5).
- Compare the three formulas and use the one your clinical protocol requires.
Notes
All results are in square metres (m²), rounded half-up to 2 decimals. The calculation assumes height in centimetres and weight in kilograms.
Sources
References
- [1]Simplified Calculation of Body-Surface AreaMosteller RD, N Engl J Med, 1987
- [2]Clinical Calorimetry, Tenth Paper: A Formula to Estimate the Approximate Surface Area if Height and Weight Be KnownDu Bois D, Du Bois EF, Arch Intern Med, 1916
- [3]Geometric method for measuring body surface area: A height-weight formula validated in infants, children, and adultsHaycock GB, Schwartz GJ, Wisotsky DH, J Pediatr, 1978
Frequently asked questions
BSA is used to dose some drugs such as chemotherapy, to calculate values like the cardiac index (cardiac output ÷ BSA) and to normalise kidney function results to the standard surface of 1.73 m².
In adults Mosteller, Du Bois and Haycock give very similar results. Mosteller is the most common because it is easy to calculate; Haycock was developed for children. Which formula applies depends on the treatment protocol.
Around 1.9 m² is common for adult men and around 1.6 m² for adult women. The 1.73 m² used in laboratory reports is the accepted standard value for an average adult.
In the Mosteller formula BSA is proportional to the square root of weight, so a 10% weight increase raises BSA by about 5%. Weight changes are therefore reflected more gently in BSA.
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