Calculates body surface area using the Mosteller formula.
Body Surface Area: Clinical Guide
Browse Knowledge HubBody surface area is an anthropometric estimate used in selected drug dosing, physiological indexing and clinical calculations.
Overview
Body surface area estimates the external surface area of the body from height and weight. MedicalC uses the Mosteller equation because it is simple and widely used.
Clinical Significance
BSA is used to index cardiac measurements, renal measures and some medication doses. It is an estimate and does not directly measure body composition or organ function.
When to Use
- Use when a protocol explicitly requires body surface area.
- Use for selected oncology, cardiology and physiological calculations.
- Confirm whether the relevant protocol requires actual, capped or adjusted BSA.
How It Is Calculated
- Mosteller formula: BSA (m²) = square root of ((height in cm × weight in kg) ÷ 3600).
- Height and weight are converted to centimetres and kilograms before calculation.
Interpretation
- The result is reported in square metres.
- There is no universal normal BSA threshold for individual clinical decisions.
- Interpret according to the protocol in which BSA is being used.
Worked Example
A person who is 170 cm tall and weighs 70 kg has a BSA of approximately 1.82 m².
Patient Considerations
- Extremes of body size, oedema, ascites, amputation and pregnancy may reduce the usefulness of an anthropometric estimate.
Limitations
- BSA is derived rather than measured.
- Different BSA equations can give slightly different results.
- BSA-based dosing may not be appropriate for every medicine or patient.
Clinical Pearls
- Use the same BSA method specified by the relevant protocol.
- Check whether dose capping is required.
- Review current height and weight rather than copied historical values.
Common Mistakes
- Entering height in metres when centimetres are expected.
- Using pounds without the correct unit conversion.
- Assuming BSA alone determines a safe medicine dose.
Evidence Base
The Mosteller equation was published as a simplified method for calculating BSA and remains widely used in clinical practice.
Frequently Asked Questions
What formula does this calculator use?
It uses the Mosteller formula.
Is BSA the same as BMI?
No. BMI relates weight to height squared, while BSA estimates external body surface area.
Can BSA determine a medicine dose by itself?
No. Follow the medicine-specific protocol and clinical assessment.
References
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317:1098. — Original publication of the simplified Mosteller equation.
Reviewed by: MedicalC Clinical Editorial Team
Last reviewed: July 2026
Clinical Disclaimer
MedicalC calculators and clinical tools are intended to support healthcare professionals. They do not replace clinical judgement, individual patient assessment, local guidance or specialist advice.
Results should always be interpreted in the context of the patient’s history, examination, investigations, current clinical condition and applicable professional guidance.