BSA Calculator
Calculate your Body Surface Area using multiple medical formulas (Du Bois, Mosteller, Haycock).
Enter Your Values
Enter your values and press Calculate: you will get the result, its method, the inputs used and confidence, plus copy, print and share options.
How this calculator works
Mosteller BSAv1.0.0
Body surface area = √(height(cm) × weight(kg) / 3600).
- Applies to
- Adults and children ≥ 2 mg/kg dosing contexts
- Assumptions
- Standard BSA application context
- Limitations
- Empirical formula; individual validity varies
- Output
- m²
- Last reviewed
- 2026-06-01
Evidence Sources & Literature
- The New England Journal of Medicine. Simplified calculation of body-surface area. N Engl J Med, 1987. doi:10.1056/NEJM198710223171717.
About the BSA Calculator
BSA (body surface area) estimates the total surface area of your body in square meters. It is not a fitness or weight metric: it is mainly a clinical tool, used by doctors and pharmacists to calculate certain medication doses (especially in chemotherapy), to gauge how the body handles fluids, and to index measures like kidney function and heart output. This calculator estimates BSA from your height and weight.
I include this one because people sometimes encounter BSA in a medical setting and want to understand it. It is genuinely a clinical number, so I will explain what it is for honestly, and stress that dosing decisions always belong to your medical team.
What BSA is used for
Body surface area is widely used in medicine because many physiological processes scale better with surface area than with weight alone. Doctors use it to calculate doses of certain drugs (chemotherapy is the classic example), to estimate fluid needs in burns care, and to index measures such as the glomerular filtration rate (kidney function) and cardiac index (heart output). It gives a more standardized basis than weight for these specific calculations.
How it is estimated
BSA cannot be measured directly in everyday practice, so it is estimated with validated formulas that use your height and weight. Several formulas exist (the Du Bois and Mosteller equations are common), and they give very similar results for most people. This calculator applies a standard formula to produce an estimate in square meters. For an average adult, BSA usually lands somewhere around 1.7 square meters, give or take.
Why doctors prefer it for some doses
For drugs with a narrow margin between an effective and a harmful dose, scaling by body surface area can match the dose more closely to how the body actually processes the medication than scaling by weight alone. That precision is why BSA-based dosing is standard in oncology. It is a good example of a number that is highly useful in expert hands and not something to act on yourself.
An important boundary
I want to be very clear: this calculator is for education and general understanding only. If you are looking at BSA in connection with a medication dose or a medical test, those decisions must be made by your doctor or pharmacist using your full clinical picture. Never adjust a dose based on a number from any online calculator. Use this to understand the concept, and leave the application to your medical team.
Dietitian Insight: Body surface area (BSA) provides an accurate physiological metric for clinical drug dosing and cardiac output indices. Learn about physiological surface area and metabolic demands, and compare metrics with our body mass index calculator.
Sources & method
This calculator uses established, peer-reviewed formulas and reference ranges from recognized health and nutrition authorities. Results are estimates for general education, not a medical diagnosis. For decisions about your health, consult a qualified clinician. Reviewed by Macro & Meals Editorial Team, Content editor.
Frequently Asked Questions
What is body surface area used for?
BSA is mainly a clinical measure. Doctors use it to calculate doses of certain medications (notably chemotherapy), to estimate fluid needs, and to index measures like kidney function and heart output. Many physiological processes scale better with surface area than with weight alone.
How is BSA calculated?
It is estimated from your height and weight using validated formulas such as the Du Bois or Mosteller equations, which give very similar results for most people. This calculator applies a standard formula to produce an estimate in square meters; an average adult is often around 1.7 square meters.
What is a normal body surface area?
For an average adult, BSA typically falls around 1.7 square meters, though it varies with height and weight. There is no single right value; it simply reflects your size and is used as a basis for specific clinical calculations rather than as a health target.
Can I use BSA to work out my own medication dose?
No. BSA-based dosing must be done by your doctor or pharmacist using your full clinical picture. This calculator is for education only, to help you understand the concept. Never adjust any medication dose based on an online calculator.
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