Use this free surface area body calculator to estimate your body surface area (BSA) from height and weight. BSA is commonly used in medicine for medication dosing, fluid planning, and clinical assessments.
Body Surface Area (BSA) Calculator
Enter your measurements, choose a formula, and click calculate.
What is body surface area (BSA)?
Body surface area is an estimate of the total external area of the human body, usually expressed in square meters (m²). Unlike BMI, which focuses on body mass relative to height, BSA attempts to capture physical body size in a way that can be useful for clinical decisions.
Why BSA matters in healthcare
- Medication dosing: Some drugs, especially chemotherapy agents, are prescribed per m².
- Kidney and cardiac assessments: Certain values are indexed to BSA for fair comparison across body sizes.
- Burn care: Surface-related estimates can support treatment planning.
- Pediatric medicine: BSA can sometimes provide better dosing precision than weight alone.
Formulas included in this calculator
There is no single “perfect” formula. Different formulas were developed from different populations and methods. For most healthy adults, the values are similar and usually differ by only a small margin.
1) Mosteller formula
BSA = √((height in cm × weight in kg) / 3600)
This is one of the most widely used formulas due to its simplicity and practical accuracy.
2) Du Bois & Du Bois formula
BSA = 0.007184 × height(cm)0.725 × weight(kg)0.425
A classic formula that remains common in research and older clinical references.
3) Haycock formula
BSA = 0.024265 × height(cm)0.3964 × weight(kg)0.5378
Often used in pediatric settings and studies.
4) Gehan & George and Boyd formulas
These formulas are additional validated options. They can be useful when comparing outputs across methods or when matching a specific institutional protocol.
How to measure accurately
- Measure height without shoes, standing upright against a wall.
- Measure weight with light clothing, ideally at a consistent time of day.
- Use the same units each time to track changes reliably.
- If possible, repeat each measurement and average the values.
How to interpret your result
Adult BSA often falls roughly between 1.5 and 2.2 m², but normal values vary by sex, body composition, and population. A higher or lower number does not automatically indicate good or bad health. It is simply a body-size estimate.
Example calculation
If someone is 170 cm tall and weighs 70 kg, the Mosteller estimate is approximately 1.82 m². Other formulas may produce values close to this, typically within a few hundredths of a square meter.
Surface area body calculator FAQ
Is BSA the same as BMI?
No. BMI estimates weight status, while BSA estimates external body size area.
Which formula should I use?
Mosteller is a common default. If your clinic, school, or protocol specifies a formula, use that one for consistency.
Can I use imperial units?
Yes. This calculator accepts inches and pounds and converts them to metric automatically before applying formulas.
Can I use this for children?
It can provide an estimate, but pediatric dosing and interpretation should always be reviewed by qualified clinicians.
Bottom line
A surface area body calculator gives a fast, practical BSA estimate that can support education and clinical planning. For any treatment or dosing decision, always confirm with a licensed healthcare professional.