Body Surface Area Calculator

Calculate your Body Surface Area (BSA) using Du Bois, Mosteller, or Haycock formulas.

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Body Surface Area (BSA) estimates total skin surface in square metres. Average adult: 1.7 m² (women) and 1.9 m² (men). Du Bois formula (1916) is the clinical standard; Mosteller gives near-identical results with simpler maths; Haycock is preferred for children. BSA is used for chemotherapy dosing, cardiac index, burn assessment (Rule of Nines), and GFR normalisation.

Enter weight and height in metric or imperial to calculate BSA using your preferred formula.

Units

Weight (kg)

Height (cm)

Formula

Educational Estimates Only: These calculations are approximations based on population-level formulas and may not accurately reflect your individual health status. Body composition varies significantly due to factors like muscle mass, bone density, hydration, and ethnicity. This is not medical advice. Always consult a qualified healthcare provider for personalized assessment, diagnosis, or treatment decisions.

Methodology and sources

Formula or method

Calculates body surface area from height and weight using the Du Bois, Mosteller, or Haycock formula selected in the calculator.

Basis and assumptions

Metric inputs are used internally: height in centimetres and weight in kilograms.
Du Bois applies a power equation; Mosteller uses the square root of height times weight divided by 3600.
Haycock is included because the tool names it as preferred for paediatric use.
BSA is an estimate of body size and should not drive dosing decisions without clinical review.

What this tool does not decide

Medication dosing, chemotherapy dosing, burn treatment, cardiac assessment, or kidney assessment. Consult a doctor, pharmacist, or healthcare professional.
Which BSA formula a clinician should use for a specific adult, child, or specialist treatment protocol.

Sources

Du Bois & Du Bois (1916), Arch Intern Med 17:863-871
Mosteller (1987), N Engl J Med 317:1098
Haycock et al. (1978), J Pediatr 93:62-66

Last checked: 2026-06-05

What Is Body Surface Area Used For?

Body Surface Area (BSA) estimates the total area of skin covering your body. It sounds like a trivial measurement, but it's critical in medicine, far more than you'd expect.

Oncologists use BSA to calculate chemotherapy drug dosages. The more surface area you have, the more drug you need. Getting this wrong by even 10% can mean the difference between an effective dose and a toxic one. BSA is also used for cardiac index calculations (how efficiently your heart pumps relative to your body size), burn assessment, and kidney function analysis.

For the average person, BSA isn't something you need to track like BMI or body fat. But if you're curious about how your body compares to population averages, or if a medical professional has mentioned your BSA, this calculator gives you the number in seconds.

The Three BSA Formulas

Formula	Year	Equation	Best For
Du Bois	1916	0.007184 x H^0.725 x W^0.425	Most widely used in clinical practice
Mosteller	1987	√(H x W / 3600)	Simplest calculation, very similar results
Haycock	1978	0.024265 x H^0.3964 x W^0.5378	More accurate for children and infants

What this means for you: For adults, all three formulas give results within 2 to 3% of each other. Du Bois is the clinical standard, Mosteller is the simplest to calculate by hand, and Haycock is preferred for paediatric use. H = height in cm, W = weight in kg.

Average BSA by Sex and Height

Height	Average Male BSA	Average Female BSA
160 cm / 5'3"	1.72 m²	1.60 m²
170 cm / 5'7"	1.85 m²	1.71 m²
175 cm / 5'9"	1.91 m²	1.76 m²
180 cm / 5'11"	1.98 m²	1.82 m²
190 cm / 6'3"	2.11 m²	1.94 m²

Values assume average weight for each height. The global average adult BSA is approximately 1.7 m² for women and 1.9 m² for men.

Medical Applications of BSA

Chemotherapy Dosing

Most chemotherapy drugs are dosed in mg/m² of BSA. This ensures that larger patients receive proportionally more drug, reducing under-dosing in large patients and toxicity in small patients.

Cardiac Index

Cardiac output (litres/min) divided by BSA gives the cardiac index, a normalised measure of heart function. Normal is 2.5 to 4.0 L/min/m². This allows comparison of heart performance across different body sizes.

Burn Assessment

The "Rule of Nines" estimates burn area as a percentage of BSA. Head = 9%, each arm = 9%, each leg = 18%, front torso = 18%, back = 18%. Fluid replacement in burn patients is calculated using BSA percentage.

Kidney Function (GFR)

Glomerular filtration rate (GFR) is normalised to a standard BSA of 1.73 m². This allows meaningful comparison of kidney function between individuals of different sizes.

Worked BSA Example

Suppose an adult weighs 70 kg and is 175 cm tall. The three formulas in this tool all use the same two inputs, but they weight height and mass slightly differently.

Formula	How the inputs are used	Practical reading
Du Bois	Power equation using height and weight	Traditional clinical reference formula
Mosteller	Square root of height times weight divided by 3600	Simple formula for quick manual checking
Haycock	Power equation with different exponents	Often preferred when paediatric context matters

Small differences between formulas are normal. If a BSA value is being used for medicines, scans, cardiac index, or renal assessment, the clinical protocol should specify which formula is appropriate.

When Formula Choice Matters

Routine Adult Estimate

For typical adult height and weight ranges, Du Bois and Mosteller usually sit close together. A small difference is rarely meaningful unless a dosing rule is very sensitive.

Children and Infants

Haycock is included because the tool notes its paediatric use. Children should never have treatment decisions based on a web estimate alone.

Very High or Low Body Weight

Extreme body sizes can make any formula less representative. Clinical teams may cap BSA, use adjusted body weight, or choose a protocol-specific method.

Medicine Dosing

Oncology, nephrology, and cardiology teams often use BSA inside a wider protocol. The calculator can help you understand the maths, but not choose a dose.

How to Use a BSA Result Safely

Check that height and weight were entered in the intended units. A pounds versus kilograms mix-up changes the result dramatically.
Keep the selected formula visible when sharing the result. A value without a formula name can be ambiguous.
Treat the classification as context, not as a diagnosis. BSA mainly describes body size, not health status.
For medication, chemotherapy, burn care, kidney function, or cardiac output, ask the responsible clinician which formula and protocol they use.

BSA Result Review Checklist

Before copying a BSA value into notes or a message, review the calculation context so the number is not detached from its assumptions.

Confirm whether the result came from Du Bois, Mosteller, or Haycock.
Keep the original height and weight beside the result for traceability.
Repeat the calculation after a major weight change.
Ask the clinical team before using BSA for any dose, infusion, or protocol decision.

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How to use this tool

Enter weight and height

Choose Du Bois, Mosteller, or Haycock

Calculate your BSA and classification

Common uses

Calculating medication dosages in oncology
Assessing cardiac output and cardiac index
Estimating burn surface area for treatment
Adjusting drug doses for body size
Renal function assessment

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Frequently Asked Questions

What is Body Surface Area (BSA)?

BSA estimates the total surface area of the human body in square metres. It's one of the most important measurements in clinical medicine, used for drug dosing, cardiac assessment, and burn evaluation.

Which BSA formula is most accurate?

The Du Bois formula (1916) remains the most widely used and cited. The Mosteller formula gives very similar results with simpler maths. The Haycock formula is preferred for children and infants.

What is a normal BSA?

Average adult BSA is approximately 1.7 m² for women and 1.9 m² for men. Values typically range from about 1.5 to 2.2 m² depending on height and weight.

Why do doctors use BSA instead of weight for drug dosing?

BSA correlates better with metabolic rate and organ function than weight alone. Two people with the same weight but different heights have different metabolic rates. BSA accounts for both dimensions, making drug dosing more precise, especially for chemotherapy.

How is BSA used in cancer treatment?

Most chemotherapy drugs are dosed per square metre of body surface area (e.g., 175 mg/m²). This standardises dosing across patients of different sizes, reducing the risk of underdosing or toxic overdosing.

How is BSA used in burn assessment?

Burns are classified by the percentage of total BSA affected. The Rule of Nines estimates burns quickly (each arm is 9%, each leg is 18%, etc.), and total BSA helps calculate fluid resuscitation needs using the Parkland formula.

What is the cardiac index?

Cardiac index is cardiac output divided by BSA (litres per minute per m²). A normal cardiac index is 2.5 to 4.0 L/min/m². It normalises heart function across body sizes, making it more useful than raw cardiac output for comparing patients.

How does BSA relate to kidney function?

Glomerular filtration rate (GFR) is normalised to a standard BSA of 1.73 m². This allows kidney function to be compared meaningfully across patients of different sizes.

Does BSA change with weight loss or gain?

Yes. BSA increases with both height and weight, so significant weight changes will alter your BSA. This is clinically important, patients on BSA-dosed medications may need dose adjustments after major weight changes.

Are BSA formulas accurate for very obese patients?

Standard formulas become less accurate at extreme body weights. For obese patients (BMI above 40), some clinicians use adjusted body weight or cap BSA at 2.0 m² for drug dosing to avoid toxicity.

What's the difference between Du Bois and Mosteller formulas?

Du Bois uses a power equation (height^0.725 × weight^0.425 × 0.007184) while Mosteller uses a simpler square root (√(height × weight / 3600)). Results differ by less than 1% for most adults.

Can I calculate BSA for children?

Yes, but use the Haycock formula, it was specifically validated for paediatric patients from preterm infants to adolescents. Du Bois and Mosteller were validated primarily on adults.

Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.