Body Surface Area Calculator (BSA)
By Santaji GadepatilinUpdated October 27, 2026
Body surface area is used in medicine to dose certain drugs and to compare measurements between patients of different sizes.
How to use the body surface area calculator
Enter height and weight in any units. Body surface area is shown in m² (or switch units).
The formula (Mosteller)
BSA (m²) = √(height (cm) × weight (kg) ÷ 3600)
Worked example
Height 175 cm, weight 70 kg:
BSA = √(175 × 70 ÷ 3600) = √3.403 = 1.84 m²
Other formulas
| Formula | Result for 175 cm, 70 kg |
|---|---|
| Mosteller | 1.84 m² |
| Du Bois | 1.85 m² |
| Haycock | 1.85 m² |
The formulas agree closely for average-sized adults.
BSA by formula
| Height and weight | Mosteller | Du Bois | Haycock |
|---|---|---|---|
| 150 cm, 50 kg | 1.44 | 1.43 | 1.45 |
| 160 cm, 60 kg | 1.63 | 1.62 | 1.64 |
| 170 cm, 70 kg | 1.82 | 1.81 | 1.83 |
| 175 cm, 80 kg | 1.97 | 1.96 | 1.98 |
| 185 cm, 95 kg | 2.21 | 2.19 | 2.22 |
| 110 cm, 18 kg | 0.74 | 0.74 | 0.74 |
The formulas agree closely for typical adults. Haycock was developed with children included and is often preferred in paediatrics.
Typical BSA values
| Group | Average BSA |
|---|---|
| Newborn | 0.25 m² |
| Child, 10 years | 1.1 m² |
| Adult woman | 1.6 m² |
| Adult man | 1.9 m² |
Where BSA is used
- Chemotherapy: many cancer drug doses are given per m² of BSA.
- Cardiac index: cardiac output divided by BSA, to compare heart function between people of different sizes.
- Kidney function: GFR is often reported per 1.73 m², the BSA of an average adult.
- Burns: the extent of burns is estimated as a percentage of total body surface.
Units
BSA is in square metres. The Mosteller formula uses height in centimetres and weight in kilograms. If you enter feet, inches or pounds, the calculator converts them for you.
Important
This tool is for information and education. Medicine dosing must always be done by qualified healthcare professionals using approved protocols.
Frequently asked questions
What is body surface area used for?
Doctors use BSA to calculate doses of some medicines (such as chemotherapy), to index cardiac output and kidney function, and to assess burns.
What is a normal BSA?
About 1.9 m² for adult men and 1.6 m² for adult women on average.
Which formula is used here?
The Mosteller formula (1987), BSA = √(height cm × weight kg ÷ 3600). It is simple and widely used in clinical practice.
Why is GFR adjusted to 1.73 m²?
1.73 m² is the average BSA of adults in early studies. Adjusting to it lets doctors compare kidney function between people of different sizes.
Can I use BSA to dose medicine at home?
No. Dosing by BSA is done by doctors and pharmacists for specific drugs. Always follow your prescription.