BSA Calculator: Calculate Your Body Surface

A BSA Calculator (Body Surface Area Calculator) is a free online calculator that uses your height and weight to estimate the surface area of your whole body. Body Surface Area (BSA) is often measured in square meters (m 2) and is utilised in the health care industry.

Body Surface Area does not take into account your body weight to height ratio, like Body Mass Index (BMI) would, but instead estimates the area of your body that would be exposed. This can give healthcare professionals another way to assess individuals.

BSA calculations are often used in hospitals, oncology departments, research or other medical areas throughout the United States. Some chemotherapy drugs are prescribed depending on the dosage (per square meter).

With our BSA Calculator you can easily calculate your body surface area using the standard measurements. Just enter your height and weight in either imperial (feet, inches and pounds) or metric (centimeters and Kilograms).

The calculator uses popular formulas including the Mosteller formula to give you an instant result.

Important: This is a medical measurement and should not be used as an indication of your overall health. When calculating medication dosages or treatment, you must check with a qualified healthcare professional.

How to use the BSA Calculator

To use this Body Surface Area Calculator simply enter your height and current weight.

Steps to calculate your BSA:

Choose your unit of measurement.

US Customary – Your height will be in feet and inches and weight in pounds (lbs).

Metric – Your height will be in centimeters (cm) and weight in kilograms (kg).

Enter your height.

Enter your current height.

Enter your weight.

Click calculate to calculate your BSA using your chosen formula.

View your results.

You will normally get a result in square meters (m 2). Some calculators will also show you what formula was used and extra information about your measurements.

For the most accurate results ensure you enter accurate height and weight measurements.

BSA Calculator Formula

There are various formulas that can be used to calculate an estimate of your Body Surface Area. Depending on the formula used, the results may vary slightly.

One of the most popular formulas to use is the Mosteller formula.

Mosteller Formula

BSA = sqrt[(Height(cm) x Weight(kg))/3600]
Where:

BSA = Body Surface Area (m 2)

Height = Height of individual (cm)

Weight = Weight of individual (Kg)

3600 = Constant

sqrt = Square root

Other Common Formulas

Du Bois Formula

BSA = 0.007184 x Height 0.725 x Weight 0.425

Height = Centimeters

Weight = Kilograms

Haycock Formula

BSA = 0.024265 x Height 0.3964 x Weight 0.5378

Height = Centimeters

Weight = Kilograms

Gehan and George Formula

BSA = 0.0235 x Height 0.42246 x Weight 0.51456

Height = Centimeters

Weight = Kilograms

Whilst the formulas are all mathematically different they will give fairly similar results for most individuals.

The Mosteller formula is a good default option.

Example Calculation

Let’s look at an example to understand how the formula works.
Say we have an adult in the United States who is 175cm tall and weighs

70kg. We can use the Mosteller formula below:

BSA = sqrt[(Height x Weight)/3600]

Now plug in the numbers:

BSA = sqrt[(175 x 70)/3600]

Multiply the height by the weight:

175 x 70 = 12,250

Divide by 3600:

12,250 / 3600 = 3.4028

Now find the square root:

BSA = sqrt[3.4028]

BSA = 1.84 m 2

BSA Result Example

1.84m 2

Based on a height of 175cm, weight of 70kg and using the Mosteller formula.

Your Body Surface Area is estimated to be approximately 1.84m 2.
This is just an estimate and should not be used on its own to calculate medication.

Understanding your BSA Result

Your result shows your estimated total exposed surface area of your body.
If your result is 1.84m 2 then your Body Surface Area is estimated to be approximately 1.84m 2.

Your BSA will vary depending on your height, weight, age and other factors.

Below is an example of what BSA’s you may get as an adult:

BSA (m 2) General Meaning

1.40-1.50 Lower estimated surface area

1.51-1.70 Medium estimated surface area

1.71-1.90 Typical adult range

1.91-2.10 Higher estimated surface area

Over 2.10 Larger estimated surface area

Please note these are just examples and are not official medical references or health categories. There isn’t a perfect BSA for everyone.

Healthcare professionals will interpret your BSA depending on your age, health, treatment needs and other factors.

Also make sure you don’t confuse BSA with BMI. BMI calculates your weight to height ratio whereas BSA is an estimate of your exposed body surface area.

Factors affecting your Body Surface Area

There are many factors that will affect your Body Surface Area.
Height

Height will be one of the main factors in calculating your BSA. Taller individuals will generally have a larger BSA than those who are shorter.

Weight

Your weight will also play a big part in calculating your BSA. Those with a higher weight will generally have a higher estimated BSA.

Age

Age can affect your body size and body composition. Children, Adults and older people may have different characteristics.

It can be particularly important to calculate children’s BSA.

Body Composition

Muscle mass and body fat can affect your actual BSA but most formulas will use height and weight.

Accuracy of measurements

If you enter incorrect measurements then this can affect your results. If you can enter recent and accurate measurements this will help give more accurate results.

Medical Conditions

Some medical conditions can affect your BSA. For example fluid retention or large weight changes.

Benefits and Uses of BSA

There are many benefits to calculating your Body Surface Area.

Medication Dosage

Some medication will use BSA to calculate the dosage. For example chemotherapy drugs. Healthcare professionals may calculate the dose based on how much they need per square meter.

Dose = Prescribed Dose per m 2 x BSA

This may be adjusted depending on lab results, kidney function, treatment and other factors.

Oncoogy

BSA is commonly used in oncology to help calculate some chemotherapy dosages.

Cardiac

Sometimes BSA is used to calculate cardiovascular measurements such as cardiac output.

Kidneys

Some kidney measurements may be standardised to a BSA of 1.73m 2. This can help healthcare professionals compare kidney function.

Research

When researching, BSA is used to compare physiological measurements. This can help standardise certain measurements.

Clinical

Healthcare professionals may take this into consideration with other measurements when assessing patients, choosing treatment and tracking progress.

Accuracy, Assumptions and Limitations

A BSA Calculator will give you an estimate of your exposed body surface area.

The Mosteller formula is commonly used as it is simple and gives practical results for many patients. However it will depend on how accurate your height and weight are.

Below are some important points to note.

Estimate – Standard formulas will give you an estimate of your BSA. They won’t actually measure your skin.

Body Composition – Most formulas won’t take into account your muscle mass, body fat and shape.

Large/Small Bodies – Those with a very large or small weight may not be as accurate.

Age – Adult formulas may not be the best to use for children/neonates.
Medical Conditions – Fluid retention, oedema and other conditions can affect your weight.

Formulas – The Mosteller, Du Bois, Haycock and Gehan-George formulas may give slightly different results.

For clinical use, follow the guidelines set by your institution and medication.

Never use an online BSA result to calculate or change the dosage of a prescription medication.

FAQ’s

What does BSA mean in medical terms?

BSA stands for Body Surface Area. It is an estimated measurement of the exposed area of the human body. It is generally measured in square meters (m 2) and is used by healthcare professionals for certain medication calculations, assessments and research.

What is a normal BSA for an adult?

Many adults will have a BSA between 1.6m 2 and 2.0m 2. However this can vary greatly depending on your height, weight and body composition. There isn’t a universal normal or ideal BSA for everyone.

What is the most accurate BSA formula?

The Mosteller formula is commonly used due to it being simple and giving practical results. However there are other established formulas such as the Du Bois, Haycock and Gehan-George formulas. There isn’t a universally most accurate formula for everyone.

What is the difference between BSA and BMI?

BSA is an estimate of your exposed body surface area in square meters. BMI is a measurement of your weight to height ratio in Kg/m 2.

Can I use a BSA Calculator to calculate medication?

A BSA Calculator can be used to help you calculate the BSA used in some medication calculations. However you must never use this to calculate or change the dosage of a medication. Always follow the prescription, treatment and instructions given by a qualified healthcare professional.