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Body Surface Area (BSA) Calculator

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Body Surface Area Calculator
Calculate BSA using validated medical formulas. BSA is essential for medication dosing (especially chemotherapy), clinical assessments, and metabolic calculations.
Mosteller is the most commonly used

Mosteller Formula (1987)

BSA = √((Height(cm) × Weight(kg)) / 3600)

Most commonly used formula. Simple, accurate, and easy to calculate.

Du Bois & Du Bois (1916)

BSA = 0.007184 × Height^0.725 × Weight^0.425

Oldest and most widely validated formula.

Haycock Formula (1978)

BSA = 0.024265 × Height^0.3964 × Weight^0.5378

Often preferred for pediatric patients.

Gehan & George (1970)

BSA = 0.0235 × Height^0.42246 × Weight^0.51456

Developed for cancer patients, works well across various body sizes.

Boyd Formula (1935)

BSA = 0.0333 × Weight^(0.6157-0.0188×log(W)) × Height^0.3

Less commonly used today, more complex calculation.

About This Tool

Body Surface Area Calculator – Calculate BSA from Height and Weight

Body Surface Area (BSA) is a critical clinical metric used to normalize physiological variables and calculate precise drug dosages, particularly for chemotherapy treatments measured in mg/m². Use this BSA calculator online to compute BSA from height and weight using validated formulas including Mosteller, Du Bois, Haycock, Gehan & George, and Boyd methods.

Understanding Body Surface Area in Clinical Practice

BSA correlates with metabolic mass more accurately than body weight alone, making it essential for clinical calculations. Healthcare professionals rely on BSA calculator for chemotherapy dosing, cardiac index measurements, and normalizing renal function (e.g., GFR per 1.73 m²). The Mosteller BSA calculator is the most widely adopted formula due to its simplicity and proven accuracy across both adult and pediatric populations.

Unlike simple weight-based calculations, BSA provides a more physiologically relevant measure for drug distribution, metabolic rate, and organ function assessment. This makes it indispensable in oncology, critical care, and pediatric medicine where precise dosing can mean the difference between therapeutic success and toxicity.

Step-by-Step BSA Calculation Examples

Example 1 – Mosteller Formula (Metric)

Patient: Height 170 cm, Weight 70 kg

Mosteller formula: BSA = √((height_cm × weight_kg) / 3600)

Step 1: Multiply height × weight
170 × 70 = 11,900

Step 2: Divide by 3600
11,900 ÷ 3600 = 3.3056

Step 3: Calculate square root
√3.3056 = 1.818 m² (≈ 1.82 m²)

Clinical application: If a chemotherapy protocol prescribes 75 mg/m², the total dose would be 75 × 1.818 = 136.4 mg. This precision is crucial for balancing efficacy against toxicity in oncology treatments.

Example 2 – Imperial Units

Patient: Height 5'7" (67 inches), Weight 154 lbs

Step 1: Convert to metric
67 inches × 2.54 = 170.18 cm
154 lbs ÷ 2.205 = 69.9 kg

Step 2: Apply Mosteller formula
BSA = √((170.18 × 69.9) / 3600)
BSA ≈ 1.82 m²

This demonstrates how the calculator handles both metric and imperial measurements seamlessly—essential for international clinical practice and ensuring consistent dosing regardless of measurement system.

Supported BSA Formulas and When to Use Them

  • Mosteller (1987) – Recommended default for general clinical use; simple, accurate, and validated across wide age ranges
  • Du Bois & Du Bois (1916) – Historical standard used in research comparisons and epidemiological studies
  • Haycock (1978) – Often preferred for BSA calculator pediatric applications due to superior accuracy in children
  • Gehan & George (1970) – Alternative validated method with strong performance in diverse populations
  • Boyd (1935) – Additional option for cross-verification in research settings

Pro tip: Compare results across multiple formulas to assess variability. Most formulas agree within 2–5% for average adults, but differences can widen at extremes (neonates, infants, or patients with severe obesity).

Clinical Applications of BSA Calculations

  • Chemotherapy dosing – Most cytotoxic agents are dosed in mg/m² to normalize therapeutic effect and minimize toxicity
  • Cardiac index – Cardiac output normalized to BSA (L/min/m²) for assessing cardiac function
  • Renal function – GFR indexed to standard BSA (1.73 m²) for consistent kidney function assessment
  • Pediatric dosing – Many medications require BSA-based calculations for children
  • Clinical trials – BSA normalization allows comparison across diverse patient populations

Clinical disclaimer: This BSA calculator is designed for estimation and educational purposes. It should not replace professional medical judgment. For dosing in extreme body sizes, burns, edema, or special populations, always consult clinical guidelines or a clinical pharmacist. Always verify calculated doses against institutional protocols.

Our body surface area calculator online is designed for accuracy, ease of use, and accessibility. Whether you're a healthcare professional needing quick BSA calculations for medication dosing, a researcher working with normalized physiological data, or a student learning clinical calculations, this tool provides instant, reliable results with full support for both metric and imperial units.

Frequently Asked Questions

Is the Body Surface Area (BSA) Calculator free?

Yes, Body Surface Area (BSA) Calculator is totally free :)

Can I use the Body Surface Area (BSA) Calculator offline?

Yes, you can install the webapp as PWA.

Is it safe to use Body Surface Area (BSA) Calculator?

Yes, any data related to Body Surface Area (BSA) Calculator only stored in your browser (if storage required). You can simply clear browser cache to clear all the stored data. We do not store any data on server.

What is Body Surface Area (BSA)?

Body Surface Area (BSA) is a measurement of the total surface area of the human body, typically expressed in square meters (m²). It's an important metric in medicine used for calculating medication dosages, determining cardiac index, assessing burn severity, and other clinical applications. BSA takes into account both height and weight, providing a more accurate measure than weight alone for certain medical calculations.

Which BSA formula is most accurate?

The Mosteller formula is the most commonly used and recommended formula because it's simple, accurate, and easy to calculate. It was published in 1987 and is the default formula used in most clinical settings. The Du Bois formula (1916) is the oldest and widely validated, while Haycock (1978) is often preferred for pediatric patients. The choice of formula can vary slightly (typically within 2-5%), but Mosteller is generally considered the standard.

Why is BSA important for medication dosing?

BSA is crucial for medication dosing, especially in chemotherapy and other potent drugs, because it provides a more accurate way to calculate safe and effective doses than body weight alone. Many medications, particularly cancer drugs, are dosed per square meter of body surface area (e.g., mg/m²). This approach accounts for metabolic rate and drug clearance, which correlate better with BSA than with weight, reducing the risk of under-dosing or toxicity.

What is a normal BSA for adults?

The average BSA for adults ranges from 1.5 to 2.0 m². For adult males, the average is approximately 1.9 m² (range: 1.7-2.1 m²), while for adult females, it's approximately 1.6 m² (range: 1.4-1.8 m²). However, BSA varies significantly based on height, weight, and body composition. Children have much lower BSA values, ranging from 0.5 m² for infants to approaching adult values in adolescence.

Can I use BSA to calculate calorie needs?

Yes, BSA can be used to estimate basal metabolic rate (BMR) and calorie needs, though this is less common than using weight-based formulas. The relationship is approximately 1500-1800 kcal per m² of BSA per day for maintenance. However, for practical purposes, most nutritionists and dietitians prefer formulas like Harris-Benedict or Mifflin-St Jeor that directly calculate calorie needs from height, weight, age, and activity level.

How do different BSA formulas compare?

Most BSA formulas produce results within 2-5% of each other for average-sized adults. Mosteller tends to give slightly lower values than Du Bois for larger individuals. Haycock is often preferred in pediatrics as it's more accurate for children. Gehan & George was developed for cancer patients and works well across a wide range of body sizes. Boyd is less commonly used today. For clinical purposes, the differences are usually clinically insignificant, and consistency in formula choice matters more than which specific formula is used.