Body Surface Area Calculator
Estimate body surface area from height and weight using the Mosteller and Du Bois formulas.
The Mosteller estimate is the most widely used formula in clinical practice.
The Du Bois & Du Bois formula — the two estimates agree to within a few percent.
Body surface area (BSA) estimates the total area of your skin in square metres from height and weight. For a person 180 cm tall weighing 75 kg, the Mosteller formula gives BSA = √((180 × 75) ÷ 3600) = √3.75 ≈ 1.94 m², and Du Bois agrees at about 1.94 m².
What body surface area measures
Body surface area (BSA) is the total surface area of the human body, expressed in square metres (m²). Unlike body weight alone, it scales with both height and mass, so it tracks the size of the whole body more faithfully. In clinical settings BSA is often a better basis than weight for scaling physiological quantities, because organ size, blood volume, and metabolic rate correlate more closely with surface area.
Because BSA cannot be measured directly, it is estimated from height and weight using validated formulas. This calculator reports two of the most established ones — Mosteller and Du Bois & Du Bois — so you can see that they agree closely, usually to within a few percent.
Where BSA is used
BSA is central to drug dosing, especially chemotherapy, where doses are prescribed in mg per m² so the amount scales with body size. It also underpins the cardiac index (cardiac output ÷ BSA), burn assessment, glomerular filtration rate normalisation, and paediatric dosing. That makes it a routine calculation for nursing, pharmacy, and medical students.
Both return BSA in m². Height in centimetres, weight in kilograms; imperial inputs are converted first (1 in = 2.54 cm, 1 lb = 0.453592 kg).
Worked example: 180 cm, 75 kg
The Mosteller formula is quick to do by hand — multiply, divide by 3600, then take the square root:
- 1 Use metric units. Height in centimetres, weight in kilograms. 1 in = 2.54 cm; 1 lb = 0.453592 kg.
- 2 Multiply height by weight. 180 cm × 75 kg = 13,500.
- 3 Divide by 3600. 13,500 ÷ 3600 = 3.75.
- 4 Take the square root (Mosteller). √3.75 = 1.9365 ≈ 1.94 m².
- 5 Cross-check with Du Bois. 0.007184 × 180^0.725 × 75^0.425 ≈ 1.94 m² — the two formulas agree.
Typical BSA values by height and weight
Mosteller and Du Bois estimates for common adult sizes. An average adult is often quoted at roughly 1.7 m².
| Height | Weight | Mosteller (m²) | Du Bois (m²) |
|---|---|---|---|
| 152 cm | 50 kg | 1.45 | 1.45 |
| 165 cm | 60 kg | 1.66 | 1.66 |
| 170 cm | 70 kg | 1.82 | 1.81 |
| 180 cm | 75 kg | 1.94 | 1.94 |
| 183 cm | 90 kg | 2.14 | 2.12 |
| 190 cm | 100 kg | 2.30 | 2.28 |
Choosing and interpreting the result
For most purposes the Mosteller formula is preferred because it is simple enough to compute at the bedside and is the one most protocols specify. Du Bois is the classic 1916 equation and remains a common reference; the two rarely differ by more than about 3%, so either is defensible. Some centres cap chemotherapy dosing at a BSA of 2.0 m² or use adjusted body weight for very high or very low weights — always follow local protocol.
This tool is an informational estimate, not medical advice. Clinical dosing must be calculated and verified by a qualified professional using the patient’s measured height and weight and the applicable protocol.