Calculate your body surface area using the Mosteller formula and compare DuBois and Haycock estimates.
Units
cm
kg
Body Surface Area (Mosteller)
1.82m²
The Mosteller formula is widely used in clinical settings for drug dosing and medical research. It provides a reliable estimate of body surface area from height and weight.
DuBois BSA1.81 m²
Haycock BSA1.83 m²
Height170 cm
Weight70 kg
Body surface area (BSA) is used in medicine to calculate drug dosages, chemotherapy protocols, and other medical treatments. The Mosteller formula is most commonly used because it provides accurate estimates across a wide range of body sizes. BSA estimates vary slightly between formulas (DuBois, Haycock); all are considered clinically equivalent. This calculator is informational only—always follow your healthcare provider's guidance for medical dosing.
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What is the Body Surface Area Calculator?
Body surface area (BSA) is the total area of a person's skin exposed to the environment, typically expressed in square metres (m²). Unlike weight or BMI, BSA accounts for how height and weight combine to create the actual external surface—two people of the same weight can have very different BSA depending on their height. In medicine, BSA is crucial because drug dosages are often calculated per unit of body surface rather than by weight alone, ensuring doses are physiologically appropriate across different body sizes.
How it works
The calculator applies the Mosteller formula, which combines height (in centimetres) and weight (in kilograms) using a simple square-root equation. You enter your height and weight in either metric (cm, kg) or imperial (ft/in, lb) units. The tool instantly calculates your primary BSA estimate using Mosteller and displays alternative estimates (DuBois and Haycock formulas) for comparison. All three formulas are clinically validated; Mosteller is preferred because it's most accurate across diverse populations.
The Mosteller formula is a simplified, elegant equation that scales height and weight proportionally under a square root—matching the geometry of body surface. The DuBois formula, developed in 1916, uses empirical exponents (0.725 for height, 0.425 for weight) derived from cadaver measurements and fit equations. Haycock is another fit-based formula with similar exponents. All three yield results within ~5% of each other; clinical guidelines typically reference Mosteller because its simplicity and accuracy make it the de facto standard.
Examples
Input
Result
Notes
Adult male, 170 cm, 70 kg
1.83 m² (Mosteller); 1.76 m² (DuBois); 1.82 m² (Haycock)
Typical adult; BSA ~1.8–2.0 m² is common for average-build adults
Tall athlete, 190 cm, 85 kg
2.16 m² (Mosteller)
Higher BSA due to both increased height and weight; important for sport-medicine dosing
Child, 110 cm, 30 kg
1.09 m² (Mosteller)
Smaller BSA; drug dosages in paediatrics are often BSA-based to avoid overdosing relative to body size
How to use the Body Surface Area Calculator
Select your preferred units (metric: cm and kg; imperial: feet, inches, and pounds)
Enter your height accurately—measure barefoot, standing straight against a wall
Enter your current weight in the selected unit
Click or wait for automatic calculation
Read your primary BSA result (Mosteller formula) in m²
Review the secondary formulas (DuBois, Haycock) in the stats section; all are clinically valid
Benefits
Clinical gold standard—BSA is the preferred metric for drug dosing across oncology, cardiology, intensive care, and paediatrics
Accurate across body sizes—unlike weight-based dosing, BSA-based calculations account for how tall vs. short people naturally distribute mass differently
Free and instant—no waiting for medical appointments or expensive body composition tests
Supports medical decision-making—carry your BSA result to your doctor for chemotherapy, immunosuppressants, or other BSA-dosed medications
Multiple formula comparison—see how Mosteller, DuBois, and Haycock agree (they typically do), boosting confidence in your estimate
Works across age groups—BSA is used from paediatric to geriatric patients, making it a lifelong health metric
Tips & common mistakes
Common mistakes
Measuring height incorrectly—don't round; BSA is sensitive to height; use a wall and level for accuracy (1 cm matters)
Using old or inaccurate weight—weight fluctuates daily; use a consistent scale and measure at the same time of day
Confusing BSA with BMI—BSA is a geometric measure (skin surface), BMI is a weight-to-height ratio; they serve different purposes
Assuming all formulas give identical results—Mosteller, DuBois, and Haycock can differ by 5–10%; use Mosteller as your primary reference
Tips
For medication planning, always confirm your BSA with your healthcare provider before any dose calculation—this calculator is informational
Remeasure your height and weight yearly, especially if you're on long-term treatment requiring BSA-based dosing
Record your BSA in your personal health records or share it with specialists who prescribe BSA-dosed medications
Be aware that BSA-based dosing can change if your weight or height changes significantly (e.g. major weight loss or gain, surgery)
Frequently asked questions
What is a 'normal' BSA?
Average adult BSA ranges from 1.7 to 2.1 m². Children have lower BSA (0.7–1.5 m²); very large or muscular adults may exceed 2.5 m². There's no single 'normal'—context your result against your height and weight.
Why is BSA used instead of weight for drug dosing?
BSA better reflects physiological variation across body sizes. A 50 kg person and a 100 kg person differ in surface area by ~35%, not 100%—so BSA-based dosing avoids overdosing small people and underdosing large people.
Do all formulas (Mosteller, DuBois, Haycock) give the same answer?
Usually within 5%. Mosteller is simpler and most widely adopted in modern medicine. DuBois and Haycock are older but still clinically valid. If your doctor specifies a formula, use that; otherwise, Mosteller is the standard.
Should I use BSA for medication doses at home?
No. This calculator is informational. Always follow your healthcare provider's prescribed dose instructions. If your dose is BSA-based, your doctor will calculate or confirm it for you.
Does BSA change if I lose or gain weight?
Yes. Both weight and height affect BSA. A 10 kg weight gain typically increases BSA by 0.15–0.20 m². Recalculate if you're on BSA-dosed medications and have had significant weight changes.
Is this calculator accurate for obese or very muscular people?
BSA formulas are empirically validated across a wide range of body compositions. They work reliably for most people; extreme obesity or very high muscle mass may have slightly less accuracy, but the result is still clinically useful.