Body Surface Area Calculator
Body surface area (BSA) is the measured or calculated surface area of the human body. It is used in some medical drug dosing and in physiology, because certain processes scale better with surface area than with weight.
Enter your height in centimetres and weight in kilograms. The calculator uses the Mosteller formula, the most widely adopted modern method.
It is mostly a clinical reference — useful if a dose you have been given is quoted per square metre, or if you are curious how your surface area compares to your weight.
Enter your values to see the result.
How this is calculated
Body surface area (BSA) is the measured or calculated surface area of the human body. This calculator uses the Mosteller formula, the most widely adopted modern method: BSA (m²) = √(height(cm) × weight(kg) ÷ 3600). It takes the square root of height times weight divided by 3,600.
BSA matters because some processes scale better with surface area than with weight. Certain drugs — especially chemotherapy and paediatric dosing — are prescribed per square metre of BSA, because clearance and toxicity correlate better with surface area than with weight alone.
The model is a single estimation formula and does not account for body shape, body composition, or the differences between the Mosteller, Du Bois and Haycock formulas, which give slightly different numbers. It is a calculation tool only: any medication dosing must be confirmed by a qualified clinician using the full clinical context, not read off this page.
Worked example
An adult who is 175 cm tall and weighs 70 kg.
- 1Height × weight = 175 × 70 = 12,250.
- 2Divide by 3,600 = 12,250 ÷ 3,600 ≈ 3.403.
- 3BSA = √3.403 ≈ 1.85 m².
Frequently asked questions
- What is the Mosteller formula?
- BSA (m²) = √(height(cm) × weight(kg) / 3600). It is simple, well-validated, and now the most commonly used BSA formula in clinical practice.
- Why is BSA used for dosing?
- Some drugs (especially chemotherapy) are dosed per m² of BSA because clearance and toxicity correlate better with surface area than with weight alone.
- Is this a substitute for clinical dosing?
- No. This tool calculates BSA only. Any medication dosing must be confirmed by a qualified clinician using the full clinical context.
- What is the Mosteller formula?
- BSA (m²) = √(height(cm) × weight(kg) ÷ 3600). It is simple, well-validated, and now the most commonly used BSA formula in clinical practice, though Du Bois and Haycock give slightly different numbers.
- Why is BSA used for dosing?
- Some drugs, especially chemotherapy, are dosed per m² of BSA because clearance and toxicity correlate better with surface area than with weight alone. Any dosing must be confirmed by a clinician, not read off this calculator.
Related calculators
Method: Mosteller body surface area formula. No external data source. Last updated: September 2026.
These results are general estimates from established formulas and are not medical advice. They depend on the accuracy of the values you enter and on individual factors the formulas cannot capture. Consult a qualified healthcare professional before making decisions about your diet, training or treatment.