CALCULATOR
Body Surface Area Calculator
BSA from four published formulas side by side, with the average, in square metres.
Body surface area
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Body surface area is used clinically, mainly for medication dosing and assessing metabolic rate. It is a reference figure, not a health measure, and any clinical use belongs with your care team rather than a web page.
What body surface area is used for
Body surface area is the total external area of the human body, expressed in square metres. A typical adult falls between roughly 1.6 and 2.0 square metres. It cannot be measured directly in practice, so it is estimated from height and weight using published formulas.
Its main applications are clinical: dosing certain medications, particularly chemotherapy agents, and normalising physiological measurements such as cardiac index across body sizes. It is also occasionally used in metabolic research because heat loss scales with surface area rather than mass.
Four formulas are shown here because they were derived from different populations and give slightly different results. Du Bois from 1916 remains the most cited; Mosteller is the simplest and is widely used clinically because it is easy to compute. Any actual clinical use belongs with your care team, not a web calculator.
The four formulas
How they compare
| Height and weight | Du Bois | Mosteller | Haycock | Gehan |
|---|---|---|---|---|
| 160 cm, 60 kg | 1.62 m2 | 1.63 m2 | 1.63 m2 | 1.63 m2 |
| 175 cm, 75 kg | 1.90 m2 | 1.91 m2 | 1.91 m2 | 1.91 m2 |
| 185 cm, 90 kg | 2.13 m2 | 2.15 m2 | 2.15 m2 | 2.15 m2 |
For adults of typical proportions the formulas agree closely, usually within 2 percent. Differences widen at the extremes of height and weight, and in children, which is why Haycock and Mosteller are often preferred in paediatric settings.
Where body surface area is used
| Application | Why BSA rather than weight |
|---|---|
| Chemotherapy dosing | Drug clearance tracks surface area more closely than mass |
| Cardiac index | Normalises cardiac output across body sizes |
| Glomerular filtration rate | Reported per 1.73 m2 as a standard reference |
| Burn assessment | Injured area expressed as a percentage of total surface |
| Metabolic research | Heat loss scales with surface area |
Typical values
| Group | Approximate BSA |
|---|---|
| Newborn | 0.25 m2 |
| Child, 2 years | 0.5 m2 |
| Child, 9 years | 1.07 m2 |
| Adult woman | 1.6 m2 |
| Adult man | 1.9 m2 |
Body surface area is a size descriptor, not a health measure. It says nothing about body composition, fitness or risk. Any clinical application, particularly medication dosing, belongs with the clinician responsible for your care rather than a web calculator.
Frequently asked questions
What is a normal body surface area?
Which BSA formula should I use?
Why is BSA used for drug dosing?
Is BSA a measure of health?
Sources
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Archives of Internal Medicine, 1916.
- Mosteller RD. Simplified calculation of body-surface area. New England Journal of Medicine, 1987.
- Haycock GB et al. Geometric method for measuring body surface area. Journal of Pediatrics, 1978.
- Gehan EA, George SL. Estimation of human body surface area from height and weight. Cancer Chemotherapy Reports, 1970.
- National Institutes of Health, Office of Dietary Supplements. Nutrient fact sheets. ods.od.nih.gov
- NHS. Nutrition and health guidance. nhs.uk
- US Departments of Agriculture and Health and Human Services. Dietary Guidelines for Americans, 2025-2030. dietaryguidelines.gov
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General information, not medical advice. Consult a qualified professional before changing your diet, especially with a medical condition.