surface body area calculator

Use this free surface body area calculator to estimate your Body Surface Area (BSA) in square meters (m²) and square feet (ft²). BSA is commonly used in clinical settings for medication dosing, kidney function indexing, and physiological assessments.

What is body surface area (BSA)?

Body Surface Area is an estimate of the total external surface of the human body. Unlike body weight alone, BSA attempts to account for both height and weight, making it useful when scaling certain physiological values across people of different sizes.

In clinical practice, BSA is often preferred for calculations where body size matters, especially when medication response or organ function varies with patient size.

How this surface body area calculator works

Step 1: Enter your height and weight

You can use either metric or imperial units. If you choose imperial, the calculator converts values internally to kilograms and centimeters before applying your selected formula.

Step 2: Choose a BSA formula

• Mosteller: BSA = √((height in cm × weight in kg) / 3600)
• Du Bois & Du Bois: BSA = 0.007184 × height^0.725 × weight^0.425
• Haycock: BSA = 0.024265 × height^0.3964 × weight^0.5378
• Gehan & George: BSA = 0.0235 × height^0.42246 × weight^0.51456

Step 3: Review your result

The tool reports your BSA in m² and ft². It also shows comparison values from the other formulas, since different methods can produce slightly different estimates.

Common uses of BSA

• Medication dosing: Some therapies (especially in oncology) are prescribed as mg/m².
• Kidney metrics: Estimated kidney function may be normalized to 1.73 m².
• Cardiology and critical care: Certain hemodynamic values can be indexed by BSA.
• Clinical research: BSA is often used for standardization across participants.

Example calculation

Suppose a person weighs 70 kg and is 175 cm tall. Using the Mosteller equation:

BSA = √((175 × 70) / 3600) = √(3.4028) ≈ 1.84 m²

That same person may get slightly different results with Du Bois or Haycock formulas. This is normal and expected.

Tips for better accuracy

• Measure height without shoes, standing upright against a wall.
• Use a recent weight measurement.
• Keep unit selection consistent with your entries.
• If using imperial units, include both feet and inches.

Limitations to remember

BSA is still an approximation. It does not directly measure body composition, fat distribution, or lean mass. In very muscular, obese, frail, pediatric, or critically ill populations, clinicians may prefer adjusted methods depending on the decision being made.

Always follow clinical guidelines and professional recommendations when BSA is used for diagnosis or treatment.

Frequently asked questions

Is BSA the same as BMI?

No. BMI estimates body mass relative to height, while BSA estimates body surface area. They are used for different purposes.

Which formula is best?

Mosteller is popular because it is simple and practical. Other formulas may be preferred in specific medical contexts. If your clinician or protocol specifies a formula, use that one.

Can I use this calculator for children?

The calculator can compute values for any valid height and weight, but pediatric interpretation should be handled by a qualified healthcare professional.