Body Surface Area (BSA) Calculator

Calculate body surface area using multiple formulas - useful for medication dosing, metabolic assessments, and medical research.

Important Disclaimer: This calculator is for informational purposes only and should be used under the guidance of a healthcare professional. Medication dosing based on BSA should be performed by qualified healthcare providers. Different formulas may yield slightly different results.
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About This Calculator

This calculator provides estimates of body surface area using five common formulas:

  • Mosteller (1987): The most widely used formula due to its simplicity and accuracy.
  • Du Bois & Du Bois (1916): One of the earliest and still widely referenced formulas.
  • Haycock (1978): Often preferred for pediatric patients.
  • Gehan & George (1970): Developed with a large reference population.
  • Boyd (1935): May be more accurate for patients with obesity.
Note: These formulas provide estimates only and should be interpreted in clinical context by qualified healthcare professionals.

About Body Surface Area

Body Surface Area (BSA) is a calculated measurement of the total surface area of the human body. It is commonly used in medicine to determine drug dosages, assess metabolic rates, and normalize physiological parameters across different body sizes.

Multiple formulas exist for calculating BSA, each with its own advantages in specific populations. This calculator provides results using the following formulas:

  • Mosteller formula (1987): BSA (m²) = √[(Height (cm) × Weight (kg))/3600]
  • Du Bois & Du Bois formula (1916): BSA (m²) = 0.007184 × Height (cm)0.725 × Weight (kg)0.425
  • Haycock formula (1978): BSA (m²) = 0.024265 × Height (cm)0.3964 × Weight (kg)0.5378
  • Gehan & George formula (1970): BSA (m²) = 0.0235 × Height (cm)0.42246 × Weight (kg)0.51456
  • Boyd formula (1935): BSA (m²) = 0.0003207 × Height (cm)0.3 × Weight (g)0.7285 - (0.0188 × log(Weight (g)))

The Mosteller formula is most widely used in clinical practice due to its simplicity and accuracy across diverse populations.

Why BSA Is Important in Medicine

Medication Dosing

Many medications, especially chemotherapy drugs, are dosed according to BSA rather than weight alone. This helps optimize efficacy while minimizing toxicity.

BSA-based dosing helps account for variations in metabolism, blood volume, and organ function that correlate with body size.

Cardiac Function

Cardiac output and other cardiovascular measurements are often indexed to BSA to allow comparison between individuals of different sizes.

Heart valve areas and other cardiac structures are evaluated relative to BSA to assess normality.

Renal Function

Glomerular filtration rate (GFR) is commonly standardized to BSA of 1.73 m² to allow for comparison of kidney function between individuals.

This standardization helps in diagnosing kidney disease and monitoring kidney function.

Burns Assessment

The severity of burns is often expressed as a percentage of total BSA affected.

This assessment is crucial for determining fluid resuscitation requirements and predicting outcomes in burn patients.

FAQs about Body Surface Area

No single formula is universally "most accurate" for all populations. The Mosteller formula is widely used due to its simplicity and reasonable accuracy across diverse populations. The Du Bois formula is one of the oldest but remains in use.

For specific populations:

  • Haycock formula may be better for children
  • Du Bois formula works well for average adults
  • Boyd formula may be better for obese individuals

In clinical practice, the Mosteller formula is often preferred due to its simplicity and generally good accuracy.

Average BSA values vary by age, sex, and population:

  • Adult men: approximately 1.9 m²
  • Adult women: approximately 1.6 m²
  • Children: varies significantly with age and development

BSA increases during childhood and adolescence as height and weight increase. There is no specific "normal" range for BSA as it's primarily used to normalize other measurements or calculate dosages rather than as a diagnostic measurement itself.

For many medications, especially chemotherapy drugs, the dose is calculated using the formula:

Dose = BSA (m²) × Dose factor (mg/m²)

The dose factor is a medication-specific value determined through clinical trials. Using BSA helps adjust doses for patients of different sizes to achieve similar drug concentrations in the body.

For example, if a chemotherapy protocol calls for 100 mg/m² of a drug, a patient with a BSA of 1.8 m² would receive 180 mg of the drug.

Yes, BSA correlates reasonably well with basal metabolic rate (BMR) and many physiological functions. This is one reason BSA is used for drug dosing—it helps account for differences in metabolism and elimination rates between individuals of different sizes.

However, other factors including age, sex, muscle mass, and genetic factors also influence metabolic rate and drug handling. Modern approaches to personalized medicine are increasingly considering these additional factors alongside BSA.