What Is Body Surface Area (BSA) and How Is It Calculated?

Body surface area, or BSA, is the total outer area of the body, measured in square metres. Doctors use it more often than weight alone to scale certain drug doses and to index heart and kidney measurements.

Quick answer

Enter height in centimetres and weight in kilograms. The tool shows BSA by the Mosteller formula, the one most used in medicine, and by the Du Bois formula for comparison.

The formulas

• Mosteller: BSA (m²) = √( height (cm) × weight (kg) ÷ 3600 )
• Du Bois: BSA (m²) = 0.007184 × weight^0.425 × height^0.725

For an adult who is 170 cm and 70 kg, Mosteller gives about 1.82 m². The two formulas usually differ by less than 0.05 m².

Why BSA matters

• Chemotherapy and some other drugs are dosed by milligrams per square metre.
• Cardiac index is cardiac output divided by BSA, so patients of different sizes can be compared.
• Burns assessment and kidney function use body-size indexing.

How to use the tool

1. Enter height in cm.
2. Enter weight in kg.
3. Read the Mosteller and Du Bois results.

Notes and limits

• BSA is a population-based estimate. Very obese, very thin or paediatric patients may need other approaches.
• Do not calculate a drug dose from this page. Doses must be set by a clinician or pharmacist.
• Use a recent weight; small changes shift the result by a few hundredths.

This tool is for information. It is not medical advice.