Body Surface Area Calculator: Mosteller & Du Bois Formulas (BSA)

Calculating your Body Surface Area (BSA) is a critical measurement used in many medical contexts, particularly for determining medication and chemotherapy dosages. Our BSA calculator provides an accurate estimate of your body’s total surface area using several recognized formulas, helping you and your healthcare providers make informed decisions.

Estimate your Body Surface Area (BSA) using several common formulas.

Your Details

Gender

Weight (lbs)

Height (ft)

Height (in)

BSA Comparison

Formula	m²	ft²	in²
Du Bois	--	--	--
Mosteller	--	--	--
Haycock	--	--	--
Boyd	--	--	--
Fujimoto	--	--	--
Takahira	--	--	--
Schlich	--	--	--

How to Use Our Body Surface Area Calculator

Our calculator is designed for simplicity and accuracy. To find your BSA, you’ll need to provide the following information. The tool will automatically calculate your BSA using multiple formulas once you’ve entered the details.

Gender: Select Male or Female. While some formulas don’t use gender directly, it’s important for context and for other potential health calculations.
Age: Enter your current age. This is particularly crucial for pediatric calculations, as BSA changes significantly during growth and development.
Weight: Input your current body weight. You can switch between pounds (lb) and kilograms (kg) for your convenience. Accurate weight is the most significant factor in your BSA result.
Height: Enter your current height. You can use feet and inches (ft/in) or centimeters (cm).

Understanding Your Results

The primary result of the calculator is your Body Surface Area, expressed in square meters ( $m^{2}$ ). This number represents the total external surface of your body. You’ll see results from several common formulas, giving you a comprehensive view.

Breakdown of BSA Formulas

Different formulas have been developed over the years to estimate BSA. Our calculator uses the most widely accepted ones:

Mosteller Formula: This is the most commonly used formula today due to its simplicity and accuracy. It is often the default for many clinical applications, including chemotherapy dosing.
- Formula: $BS A (m^{2}) = s q r t f r a c He i g h t (c m) t im es W e i g h t (k g) 3600$
Du Bois Formula: One of the oldest and most thoroughly validated formulas. It is slightly more complex but is considered highly reliable.
- Formula: $BS A (m^{2}) = 0.007184 t im esHe i g h t (c m)^{0.725} t im es W e i g h t (k g)^{0.425}$
Haycock Formula: This formula is often preferred in pediatrics, especially for infants and young children, as it was developed with a pediatric population in mind.
- Formula: $BS A (m^{2}) = 0.024265 t im esHe i g h t (c m)^{0.3964} t im es W e i g h t (k g)^{0.5378}$
Boyd Formula: Another complex formula that is also considered very accurate, particularly for a wide range of body sizes.
- Formula: $BS A (m^{2}) = 0.0003207 t im esHe i g h t (c m)^{0.3} t im es W e i g h t (g r am s)^{(0.7285 - 0.0188 l o g_10 W e i g h t (g r am s))}$

Why Does My BSA Matter?

Your BSA is a better indicator of metabolic mass than body weight alone. Since metabolic rate is more closely related to surface area than to weight, BSA is crucial for:

Chemotherapy Dosing: This is the most common use. Dosing chemotherapy based on BSA helps ensure the patient receives an effective amount of the drug while minimizing toxicity.
Glomerular Filtration Rate (GFR): BSA is used to “normalize” the GFR, which is a measure of kidney function. This allows for a more standardized comparison of kidney health between individuals of different sizes.
Cardiac Index: To assess heart function, the cardiac output is often divided by the BSA to calculate the cardiac index, providing a measure relative to a person’s body size.
Fluid Resuscitation in Burn Victims: The initial amount of intravenous fluids needed for a severe burn patient is often calculated based on their BSA.

Typical BSA Values

While BSA is highly individual, the table below shows average BSA values for adults. These are for reference only; your specific result is what’s important.

Category	Average BSA ( $m^{2}$ )
Adult Male	1.9 $m^{2}$
Adult Female	1.6 $m^{2}$
Child (9-10)	1.14 $m^{2}$
Child (12-13)	1.45 $m^{2}$
Infant	0.25 $m^{2}$

Frequently Asked Questions

What exactly is Body Surface Area (BSA)?

Body Surface Area (BSA) is the measured or calculated total surface area of a human body. Think of it as the total area of your skin. While it’s a simple concept, it’s a powerful metric because many physiological processes, like metabolism and heat loss, are more closely tied to surface area than to simple body weight. For this reason, it’s a vital measurement in medicine for calculating dosages and indexing physiological parameters.

Why use BSA for chemotherapy instead of just weight?

Using only body weight for chemotherapy dosing can be inaccurate and dangerous. A very tall, lean person and a very short, obese person might have the same weight, but their body compositions and metabolic rates are vastly different. Dosing based on weight alone could lead to underdosing the tall person (making the treatment ineffective) or overdosing the short person (causing severe toxicity). BSA provides a more accurate reflection of the body’s metabolic mass, allowing for a more standardized and safer dose of potent chemotherapy drugs. It helps ensure the concentration of the drug in the bloodstream is therapeutic but not overly toxic.

Which BSA formula is the most accurate?

There is no single “best” formula for everyone, but the Mosteller formula is currently the most widely used and accepted for its simplicity and reliable accuracy in adult populations. It’s easy to calculate and has shown strong correlation with more complex formulas. The Du Bois formula is historically significant and still considered a gold standard for validation. For pediatric patients, the Haycock formula is often preferred as it was specifically developed using data from infants and children. Our calculator provides results from multiple formulas to give a comprehensive picture.

How does obesity affect BSA calculations?

Obesity significantly increases BSA. However, there is an ongoing debate in the medical community about “dose capping” for obese patients receiving chemotherapy. Some evidence suggests that the fat tissue in obese individuals is less metabolically active and has poorer blood supply compared to lean tissue. Therefore, a full BSA-calculated dose might be excessive and lead to higher toxicity. Many oncology guidelines now recommend using an “ideal body weight” or a “capped” BSA value for obese patients to balance efficacy and safety, though this practice is not universally standardized. Always consult with a healthcare professional for dosing decisions.

Can I use this calculator for my child?

Yes, you can use this calculator for a child. For pediatric calculations, it’s especially important to have an accurate height and weight. The Haycock formula is often considered more precise for children and infants, so pay close attention to that result. BSA is used in pediatrics for many of the same reasons as in adults, including dosing for chemotherapy, certain antibiotics, and cardiovascular medications.

What is the difference between BSA and BMI?

BSA and Body Mass Index (BMI) are two different metrics that measure different things.

BSA (Body Surface Area): Measures the total surface area of your body in square meters ( $m^{2}$ ). It’s primarily a clinical tool used to calculate drug doses and assess metabolic function.
BMI (Body Mass Index): Is a measure of body fat based on your weight in relation to your height. It’s used as a general screening tool to categorize individuals into weight status groups (underweight, normal weight, overweight, obese). Essentially, BSA is about physiological function and dosing, while BMI is about assessing weight status and health risk.

How is BSA measured directly?

Direct measurement of BSA is extremely difficult and impractical for clinical use. Historically, it was done by carefully coating the body (or a cadaver) in a material of known thickness and area, like a varnish or foil, and then measuring the area of that coating. This process is obviously not feasible for living patients. This is why various mathematical formulas were developed to estimate BSA based on easily obtainable measurements like height and weight. These formulas have been validated against the few direct measurements that have been performed.

Is a higher or lower BSA better?

There is no “better” or “worse” BSA. It is not a metric of health or fitness in the way that blood pressure or cholesterol levels are. Your BSA is simply a reflection of your physical size. Its value is neutral; its importance comes from its use as a tool for other medical calculations. A person with a larger body will naturally have a larger BSA, and a smaller person will have a smaller BSA. The goal is not to achieve a specific BSA number, but to know your accurate BSA so that medical treatments can be tailored precisely to you.

Concrete Example of BSA in Action

Let’s see how a BSA calculation would work for a real person.

Patient: A 45-year-old female.
Height: 5 feet 6 inches (167.6 cm)
Weight: 150 pounds (68 kg)

Using the Mosteller formula:

Formula: $BS A = s q r t f r a c He i g h t (c m) t im es W e i g h t (k g) 3600$
Plug in values: $BS A = s q r t f r a c 167.6 t im es 683600$
Calculate: $BS A = s q r t f r a c 11396.83600 = s q r t 3.1657$
Result: $BS A a pp ro x 1.78, m^{2}$

If this patient needed a chemotherapy drug dosed at $50, m g / m^{2}$ , her specific dose would be $1.78 t im es 50, m g = 89, m g$ . Another patient with a different BSA would receive a different dose, ensuring the treatment is personalized.

Can my BSA change?

Yes, your BSA will change if your weight or height changes. Height changes are usually limited to childhood and adolescence. However, your BSA will increase if you gain weight and decrease if you lose weight. This is why it’s crucial to use your current weight for any clinical calculations. If a patient is undergoing a long course of treatment and experiences significant weight fluctuation, their healthcare provider may need to recalculate their BSA and adjust their medication dosage accordingly.

Now that you have an estimate of your Body Surface Area, you might be interested in other key health metrics. Check your weight status with our BMI Calculator or find your healthy weight range with our Ideal Body Weight Calculator.

Creator

Nhi Nguyen

A versatile quality assurance professional with a proven track record testing embedded, mobile, and web applications across defense, aerospace, telecom, pharmaceuticals and medical devices. She brings deep knowledge of QA methodologies, SDLC processes, and web technologies, along with strong project planning and cross‑functional leadership skills.

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