BSA Calculator

Body Surface Area (BSA) Calculator

Estimate your total body surface area using Mosteller and other medical formulas. Supports both Metric and Imperial units.

Body Surface Area (BSA) Calculator – Estimate Your Total Body Area Accurately

The Body Surface Area (BSA) calculator is a medical tool that estimates the total area of your body’s surface in square meters (m²). This measurement is widely used in medicine to determine correct drug dosages, metabolic rate, cardiac index, and other physiological parameters that depend on body size. Whether you’re a healthcare professional or a curious individual, the body surface area calculator provides a fast and accurate way to estimate your BSA using well-established formulas like Mosteller or Du Bois.

What Is Body Surface Area (BSA)?

Body Surface Area (BSA) refers to the estimated total external surface of the human body. Unlike weight or BMI, BSA takes both height and weight into account to approximate body size in a way that correlates better with metabolic processes. It’s typically expressed in square meters (m²). The body surface area calculator simplifies this calculation by applying standardized equations used in clinical practice worldwide.

Why Is BSA Important?

BSA is essential in various medical contexts. Doctors use it to adjust medication doses for chemotherapy, antibiotics, and anesthetics. It’s also used to assess cardiac output (in L/min/m²), determine fluid requirements, and estimate metabolic heat loss. Because the ratio between surface area and weight influences how your body processes substances, the body surface area calculator ensures precision and safety in medical dosing.

How to Use the Body Surface Area Calculator

  1. Choose your preferred unit system: Metric (cm, kg) or Imperial (inches, pounds).
  2. Enter your height and weight in the respective fields.
  3. Click Calculate to instantly view your BSA in m² according to different formulas (Mosteller, Du Bois).
  4. Compare results or use them as input for other medical or nutritional calculators.

The body surface area calculator can also help you cross-check results from related tools such as our BMI Calculator or BMR Calculator for a more complete understanding of your body metrics.

Common Formulas Used in the BSA Calculator

Several mathematical models estimate BSA. While they produce similar results, each was developed from different population studies. The body surface area calculator allows you to view at least two of the most reliable formulas:

  • Mosteller Formula (1987): BSA = √((height × weight) / 3600)
  • Du Bois and Du Bois (1916): BSA = 0.007184 × Height⁰·⁷²⁵ × Weight⁰·⁴²⁵
  • Haycock Formula (1978): BSA = 0.024265 × Height⁰·³⁹⁶⁴ × Weight⁰·⁵³⁷⁸
  • Gehan & George (1970): BSA = 0.0235 × Height⁰·⁴²²⁴₆ × Weight⁰·⁵¹⁴₅₆

All these equations aim to represent the same concept — your body’s total external surface area. Mosteller’s formula is the most common because of its simplicity and accuracy for both adults and children (PubMed: Simplified BSA Calculation).

Example Calculation

Let’s take a 175 cm, 70 kg person. Using the Mosteller formula:

BSA = √((175 × 70)/3600) = 1.84 m²

This means the individual’s body surface area is approximately 1.84 m². For comparison, the Du Bois formula gives 1.83 m² — a very close value. The body surface area calculator automates this process so you don’t need to calculate manually.

Applications of the BSA Calculator

The body surface area calculator is widely used across different medical specialties:

  • Oncology: for chemotherapy dose adjustment.
  • Cardiology: to calculate cardiac index = cardiac output / BSA.
  • Pediatrics: for fluid therapy and medication dosing in children.
  • Nutrition & Fitness: to estimate metabolic rate and caloric expenditure.
  • Pharmacology: to compare drug distribution among individuals.

BSA vs BMI – What’s the Difference?

Although both involve height and weight, they measure different things. BMI (Body Mass Index) estimates body fat relative to height, while BSA estimates surface area. For example, two people with the same BMI could have slightly different BSAs due to body proportions. The body surface area calculator provides more detailed insights for clinical applications.

Metric vs Imperial Units

Healthcare providers worldwide use both systems. In the body surface area calculator, you can easily switch between Metric (cm, kg) and Imperial (in, lb). Internally, Imperial values are converted to Metric for consistent results. This flexibility makes the tool suitable for global users.

How Accurate Is the BSA Calculator?

Accuracy depends on the chosen formula and the precision of your height and weight measurements. Studies show Mosteller’s equation deviates less than 2 % from laboratory-measured values, which is sufficient for clinical use. For medical decisions, always consult a healthcare professional (Cleveland Clinic – BSA Overview).

Children and BSA Calculations

BSA is particularly important in pediatrics. Since children vary widely in body proportions, weight alone isn’t reliable for dosing. The body surface area calculator helps physicians determine appropriate drug or IV-fluid dosages based on both height and weight. For infants, formulas like Haycock are preferred for better accuracy in smaller bodies.

BSA in Chemotherapy and Drug Dosing

Many chemotherapy drugs are prescribed per m² of body surface area. For example, a medication might be dosed at 30 mg/m². If your BSA is 1.8 m², your dose = 54 mg. Such precision ensures effectiveness while reducing toxicity risks. The body surface area calculator is therefore critical in oncology and clinical pharmacology.

How to Interpret BSA Results

Most adults have a BSA between 1.6 and 2.0 m². Larger individuals may exceed 2.2 m², while smaller or older adults may fall near 1.5 m². Children’s BSA values are significantly lower, often 0.5 – 1.3 m² depending on age and growth. The body surface area calculator gives a quick estimate that aligns closely with professional medical charts.

Using BSA in Metabolic Studies

In research and sports science, BSA helps normalize metabolic rate (kcal/m²/h) or energy expenditure. This allows fair comparison between individuals regardless of body size. Combined with our TDEE Calculator or Calorie Deficit Calculator, you can better understand how body surface influences energy balance.

Limitations of the BSA Calculator

While highly practical, the body surface area calculator is still an estimate. It doesn’t account for variations in body composition — for instance, muscular individuals may have a slightly higher true surface area than calculated. Temperature, hydration, and ethnicity can also affect results subtly. Nevertheless, BSA remains one of the best standardized measures for clinical use.

Scientific Basis Behind BSA

The relationship between height, weight, and surface area was first explored by Du Bois & Du Bois (1916). They measured 9 subjects in detail and created an equation still used today. Later studies like Mosteller’s simplified the math while maintaining accuracy. The body surface area calculator applies these validated models instantly and consistently (NIH – Du Bois Study Analysis).

Average BSA by Age and Sex

The following table provides approximate reference values for body surface area across different age groups. These ranges are estimates and can vary by population. Use the body surface area calculator to obtain your personalized value.

Age Group Average BSA – Female (m²) Average BSA – Male (m²)
Infant (0–1 yr)0.23–0.350.23–0.35
Child (2–5 yr)0.50–0.800.50–0.85
Child (6–12 yr)0.85–1.300.90–1.35
Adolescent (13–17 yr)1.30–1.651.45–1.85
Adult (18–64 yr)1.55–1.851.70–2.05
Older Adult (65+ yr)1.45–1.751.60–1.95

Advanced Uses of BSA

Beyond dosing and fluid plans, clinicians use BSA to normalize physiologic variables. For example, cardiac index (L/min/m²) allows comparison of heart function across different body sizes. Sports scientists sometimes pair BSA with TDEE Calculator to contextualize energy expenditure, while nutritionists relate BSA to resting energy needs in combination with BMR Calculator.

How to Reduce Error When Measuring BSA

  • Measure height without shoes and weight with minimal clothing.
  • Use a calibrated scale/stadiometer for accuracy.
  • Recalculate with the body surface area calculator after significant weight changes (>5–10%).
  • For children, favor pediatric-friendly formulas like Haycock when available.

BSA and Special Populations

Pregnancy: Rapid changes in weight and fluid status can affect BSA estimates; clinical oversight is recommended.
Amputations or limb differences: Standard equations may overestimate BSA; clinical adjustments or nomograms may be used.
Extremes of body composition: In very muscular or very lean individuals, BSA approximations may deviate slightly from true surface area.

Using BSA Alongside Other Health Tools

To build a comprehensive picture, combine the body surface area calculator with:

Evidence and Further Reading

Frequently Asked Questions

Which BSA formula should I use?

Mosteller is widely used for its balance of accuracy and simplicity. Du Bois is common historically. Pediatric contexts sometimes prefer Haycock. Our body surface area calculator shows at least two side-by-side.

Is BSA better than BMI?

They serve different purposes. BMI classifies weight relative to height, while BSA normalizes physiological measures and drug dosing. Use both, depending on your goal.

Should athletes use BSA?

Yes—BSA can help interpret energy use and recovery, especially when paired with TDEE and BMR for full context.

Disclaimer: The body surface area calculator is for educational purposes and does not replace medical judgment. Always consult qualified healthcare professionals for diagnosis or treatment.