Body Surface Area Calculator: Calculate Your BSA From Height and Weight

A Body Surface Area Calculator gives you a simple way to estimate the total surface area of the human body using height and weight. The result is usually expressed in square meters, written as m².

Body surface area, commonly called BSA, is different from body weight, BMI, and body fat percentage. It is mainly used as a way to describe body size and can be useful in certain medical and scientific calculations.

The CalculatorKits tool uses the Du Bois formula as its primary calculation method. You enter your weight, height, and calculation date, and the calculator provides an estimated BSA. The result area also lets you compare the Du Bois result with other established formulas, including Mosteller and Haycock.

A calculated BSA is an estimate. It is not a direct measurement of the actual surface area of your skin.

This guide explains what body surface area means, how the CalculatorKits tool works, how to use it correctly, how the main formulas differ, and why a BSA result should be interpreted carefully.

Quick Answer

A Body Surface Area Calculator estimates the approximate external surface area of your body from your height and weight.

The CalculatorKits tool uses the Du Bois formula as its main method:

BSA = 0.007184 × Weight⁰·⁴²⁵ × Height⁰·⁷²⁵

For this formula, weight is expressed in kilograms and height is expressed in centimeters. The result is expressed in square meters.

For example, a person weighing 70 kg and measuring 175 cm tall has an estimated BSA of approximately 1.85 m².

BSA is used in some clinical calculations, including certain medication dosing protocols, cardiac measurements, and kidney function assessment. However, an online calculator should never be used on its own to choose a medication dose or make a treatment decision. NIDDK explains that BSA can be relevant when interpreting kidney function for body size, while different considerations may apply when kidney function is used for drug dosing.

The CalculatorKits Body Surface Area Calculator is best used as an educational and informational tool.

What Is a Body Surface Area Calculator?

A Body Surface Area Calculator is a mathematical tool that estimates the external surface area of the human body from height and weight.

It may look similar to a BMI calculation because both use height and weight, but the purpose is different.

BMI describes body weight relative to height. BSA estimates the approximate external surface area of the body.

BSA is normally reported in square meters.

For example, a result of 1.80 m² means that the selected equation estimates the person’s body surface area to be about 1.80 square meters.

The number is not obtained by physically measuring every part of the body. Instead, it is calculated from a mathematical model.

The Du Bois and Du Bois equation is one of the best known historical methods for estimating body surface area. Later work has examined the mathematical basis of the equation and shown why height and weight based formulas are useful practical approximations rather than direct measurements.

Several other equations have also been developed. Mosteller and Haycock are two well known examples.

That is why two different body surface area calculators can sometimes return slightly different answers for the same person.

Why Use a Body Surface Area Calculator?

A Body Surface Area Calculator is useful because body weight alone does not always provide the most useful way to describe body size.

Two people can weigh the same amount but have different heights and body proportions. A height and weight based BSA estimate can provide another way to represent their size.

BSA is encountered in:

• Some medication dosing protocols

• Certain chemotherapy treatment protocols

• Cardiac index calculations

• Kidney function interpretation

• Physiological research

• Clinical education

• Scientific studies involving body size

One of the most familiar medical applications is dosing expressed in milligrams per square meter.

However, calculating BSA and calculating a medication dose are two completely different tasks. A BSA result does not tell you what medication to take or what dose is appropriate.

Clinical dosing can depend on the specific drug, treatment protocol, laboratory values, organ function, treatment history, and other patient factors. The National Cancer Institute and oncology literature also show that BSA based dosing is a clinical process rather than a simple self care calculation.

How Does the Body Surface Area Calculator Work?

The CalculatorKits tool uses height and weight to estimate body surface area.

The calculation can be understood in three simple stages.

Step 1: Enter the Correct Measurements

The main inputs are your body weight and height.

For the Du Bois formula, weight needs to be expressed in kilograms and height in centimeters.

If your weight is in pounds:

Kilograms = Pounds ÷ 2.205

If your height is in inches:

Centimeters = Inches × 2.54

The CalculatorKits interface includes unit selections to help you enter the appropriate values.

Step 2: Apply the Du Bois Formula

The primary CalculatorKits equation is:

BSA = 0.007184 × Weight⁰·⁴²⁵ × Height⁰·⁷²⁵

The fractional powers make the calculation less convenient to perform manually.

This is one reason an online Body Surface Area Calculator is useful.

Step 3: Display the Estimated BSA

After the values are entered, the tool calculates the result and displays it in square meters.

The CalculatorKits result section also provides comparison values using other established equations.

This is helpful because it shows that BSA is an estimate generated by a selected formula rather than a directly measured biological value.

How to Use the Body Surface Area Calculator

The CalculatorKits interface is straightforward. Follow these steps carefully.

1. Enter your current body weight and select the correct weight unit.
2. Enter your current height and select the correct height unit.
3. Check the calculation method displayed by the tool. CalculatorKits uses the Du Bois method as the primary calculation.
4. Confirm the calculation date if you want to keep a record of the result.
5. Review the educational and medical information shown by the calculator.
6. Click Calculate BSA.
7. Review your estimated body surface area in square meters.
8. Check the formula comparison section to see how the result compares with the Mosteller and Haycock methods.
9. Record the result and date if you are monitoring BSA over time.

Always check your units before calculating. A weight entered in pounds when kilograms are expected can produce a substantially incorrect result.

How to Calculate BSA Manually

You can calculate BSA without an online tool if you know your height and weight and have a calculator that can work with fractional powers.

The Du Bois formula is:

BSA = 0.007184 × Weight⁰·⁴²⁵ × Height⁰·⁷²⁵

Suppose a person weighs 70 kg and is 175 cm tall.

The calculation is:

BSA = 0.007184 × 70⁰·⁴²⁵ × 175⁰·⁷²⁵

The result is approximately:

BSA = 1.85 m²

This is the same basic calculation performed automatically by the CalculatorKits tool.

Manual calculation can be useful for learning, but an online tool is more convenient for everyday use and reduces the chance of arithmetic mistakes.

Du Bois Formula Explained

The Du Bois formula is one of the oldest widely recognized equations for estimating body surface area.

It is:

BSA = 0.007184 × Weight⁰·⁴²⁵ × Height⁰·⁷²⁵

The original work by Du Bois and Du Bois established a practical mathematical relationship between height, weight, and body surface area.

Later analysis found that the original type of equation remains useful for practical estimation, although its physical basis is not a perfect representation of actual body shape.

This is an important distinction.

The formula is useful because it provides a repeatable estimate.

It is not useful because it somehow measures the exact surface of every individual body.

The CalculatorKits tool uses the Du Bois equation as its primary method, so users can easily obtain the estimate without manually performing the calculation.

Mosteller Formula

The Mosteller formula is another widely used method for estimating BSA.

It is much simpler:

BSA = √[(Height in cm × Weight in kg) ÷ 3600]

Suppose the person weighs 70 kg and measures 175 cm.

The calculation becomes:

BSA = √[(175 × 70) ÷ 3600]

The result is approximately:

1.84 m²

That is very close to the Du Bois result.

Mosteller’s main advantage is simplicity. The equation is easy to calculate and has therefore become widely used in clinical environments. NIDDK also lists Mosteller among the standard equations used to calculate body surface area.

Haycock Formula

The Haycock formula is another established method for estimating BSA:

BSA = 0.024265 × Weight⁰·⁵³⁷⁸ × Height⁰·³⁹⁶⁴

Weight is measured in kilograms and height in centimeters.

The Haycock study used 81 subjects ranging from premature infants to adults and compared calculated values with geometric measurements derived from numerous body measurements. The equation was designed to perform well over a wide range of body surface areas.

This explains why Haycock is still relevant when very small body sizes are involved.

The CalculatorKits result area includes Haycock as a comparison method, giving users a chance to see how different established equations behave.

Why Do BSA Formulas Give Different Results?

A Body Surface Area Calculator can provide a slightly different result from another calculator because the formulas are not identical.

Du Bois, Mosteller, and Haycock use different mathematical relationships between height and weight.

Their underlying datasets and development methods also differ.

For typical adult measurements, the numbers are often reasonably close.

For unusual body sizes, the difference can become more noticeable.

Research comparing BSA equations has repeatedly shown that the formulas generally agree well while still producing measurable differences. This is one reason clinical settings may standardize the formula they use rather than mixing equations.

A difference between two calculators therefore does not automatically mean one of them is wrong.

It may simply mean that the calculators are using different accepted methods.

Understanding Your BSA Result

The result from a Body Surface Area Calculator is normally displayed in square meters.

For example:

1.60 m²

1.80 m²

2.00 m²

These values represent estimated body surface area.

There is no single BSA value that should be considered ideal for every person.

A taller or heavier person generally has a larger estimated body surface area than a shorter or lighter person.

The number should therefore not be treated as a health score.

It does not tell you whether you are healthy or unhealthy.

It does not directly measure body fat.

It does not directly measure muscle mass.

It is simply an estimated body size measurement created by a particular formula.

What Factors Affect Body Surface Area?

Height

Height is one of the main variables used by every common BSA formula.

As height increases, estimated BSA generally increases.

Weight

Weight also has a major influence.

As weight increases while height remains the same, estimated BSA generally increases.

Body Proportions

Two people can have the same height and weight but different body shapes.

A height and weight formula cannot fully capture these differences.

This is one reason BSA remains an estimate.

Age and Growth

Age matters most indirectly.

Children change height and body proportions rapidly, so equations may behave differently across age groups.

The Haycock study specifically included subjects ranging from premature infants to adults, partly addressing the challenge of estimating surface area across a very broad range of body sizes.

Body Surface Area vs BMI

A Body Surface Area Calculator and a BMI Calculator use similar basic measurements but provide different information.

Measurement	What It Describes	Unit
Body Surface Area	Estimated external body surface	m²
BMI	Body weight relative to height	kg/m²

BMI is primarily used as a screening measure related to weight status.

BSA is more commonly used as a body size estimate in clinical and physiological calculations.

If you want to calculate BMI separately, use the BMI Calculator.

If you are interested in body composition rather than BSA, the Body Fat Calculator provides a different type of estimate.

Why Is BSA Used in Medicine?

A Body Surface Area Calculator can be useful in medicine because some measurements are interpreted in relation to body size.

One example is cardiac index.

The general relationship is:

Cardiac Index = Cardiac Output ÷ BSA

This expresses cardiac output relative to estimated body surface area.

BSA is also used in certain medication dosing systems.

Some treatments are expressed using a dose per square meter.

This means BSA can become part of the mathematical process used to determine a treatment dose.

However, the BSA number itself is only one part of the process.

The appropriate formula, dose limits, laboratory values, organ function, treatment protocol, and patient characteristics may also matter.

That is why an online BSA result should never be treated as a prescription.

BSA and Medication Dosing

Some medications use BSA as part of their dosing method.

A simplified educational example might be:

Dose = Dose per m² × BSA

If the prescribed protocol were 100 mg/m² and the BSA were 1.80 m², the mathematical result would be 180 mg.

That example demonstrates the equation only.

It must not be used to determine a real medication dose.

NIDDK notes that clinical drug dosing can require specific kidney function estimates and that equations should be selected according to the clinical situation. It also notes that BSA adjustment may be relevant for comparing kidney function with normal values while not always being necessary for drug dosing.

BSA and Kidney Function

Body surface area is also important in kidney medicine.

Estimated glomerular filtration rate is commonly reported as:

mL/min/1.73 m²

The 1.73 m² represents a standardized body surface area.

This standardization helps compare kidney filtration between people of different body sizes.

For some clinical situations, the eGFR value may need to be adjusted for a person’s actual BSA.

NIDDK explains that BSA adjustment can be useful when comparing kidney function with normal values or CKD staging. It also explains that drug dosing can require a different approach because drug clearance is not necessarily proportional to BSA.

If you are reviewing kidney function, the GFR Calculator provides a separate educational calculation.

BSA and Chemotherapy

BSA has historically played a major role in oncology because some anticancer drugs are prescribed using BSA based dosing.

The concept can look simple:

Dose per m² × BSA = calculated dose

The clinical process is more complex.

Cancer treatment protocols can include additional considerations such as blood counts, kidney function, liver function, previous treatment, treatment toxicity, and dose limits.

Research and clinical guidance also continue to examine how BSA based dosing performs in different patient populations.

Therefore, a Body Surface Area Calculator can demonstrate the mathematics, but it should never be used to determine an actual chemotherapy dose.

Real Body Surface Area Calculator Examples

Example 1: 60 kg and 165 cm

Suppose an adult weighs 60 kg and measures 165 cm.

Using the Du Bois equation:

BSA ≈ 1.66 m²

This is a mathematical example.

Example 2: 75 kg and 178 cm

Weight: 75 kg

Height: 178 cm

Using the Du Bois equation:

BSA ≈ 1.93 m²

Example 3: 90 kg and 183 cm

Weight: 90 kg

Height: 183 cm

Using the Du Bois equation:

BSA ≈ 2.12 m²

These examples show the relationship between height, weight, and estimated BSA.

They are not medical recommendations.

How Accurate Is a Body Surface Area Calculator?

The arithmetic can be performed very precisely, but the resulting BSA is still an estimate.

That distinction is important.

The calculator can calculate:

1.848143 m²

But that does not mean a person’s true body surface area has been physically measured to six decimal places.

The equation is a mathematical model.

Actual human bodies have different shapes and proportions.

People can also have the same height and weight but different body composition.

The original Du Bois approach was practical, but later mathematical analysis has pointed out that body shape can introduce differences that a height and weight equation cannot completely capture.

Research comparing common formulas has also shown that different equations can produce different estimates, particularly at unusual body sizes.

The practical lesson is simple:

Mathematical precision is not the same as biological precision.

Does Body Composition Affect BSA?

Body composition is not directly included in the standard Du Bois equation.

The calculation uses height and weight.

Therefore, two people with exactly the same height and weight receive the same BSA estimate even if one has considerably more muscle and the other has more body fat.

This is not necessarily a flaw.

The formula is estimating body size, not body composition.

If your goal is to understand body fat, the Body Fat Calculator is more relevant.

If your goal is to estimate lean body mass, the Lean Body Mass Calculator provides a different calculation.

Can Body Surface Area Change Over Time?

Yes.

BSA can change when your height or weight changes.

Height changes are especially important during childhood and adolescence.

For adults, changes in body weight are usually the main reason the estimated value changes.

For example, if someone loses a significant amount of weight, their estimated BSA will generally decrease.

If someone gains a significant amount of weight, their estimated BSA will generally increase.

The CalculatorKits tool includes a calculation date, which can be useful when keeping records over time.

Why Is My BSA Different From Another Website?

The most common reason is the formula.

CalculatorKits uses Du Bois as its primary method.

Another website may use Mosteller.

A clinical system may use a different standard.

Rounding can also create small differences.

Unit conversion mistakes can create much larger differences.

If your hospital or healthcare professional provides a BSA value that differs from the number you get online, do not assume that the clinical value is wrong.

Ask which formula was used.

When a clinical protocol specifies a formula, that method should take priority.

Common Mistakes When Using a Body Surface Area Calculator

Entering pounds as kilograms

Always check the unit next to the weight field.

Entering inches as centimeters

The Du Bois equation requires height in centimeters.

Mixing measurement systems

Do not enter a metric weight with an unconverted imperial height.

Using old measurements

Use the relevant current measurements when a current BSA estimate is needed.

Rounding too early

If you calculate manually, excessive rounding during intermediate steps can slightly affect the result.

Comparing different formulas without checking the method

Du Bois, Mosteller, and Haycock can all produce different values.

Using an online BSA value for medication dosing

Never use a general online calculator to determine your medication dose.

Assuming more decimal places mean greater accuracy

A result with more digits is not necessarily a more accurate representation of your actual body surface area.

Body Surface Area Calculator vs Mosteller Calculator

Both methods estimate BSA from height and weight.

CalculatorKits uses Du Bois as the primary method.

The Mosteller equation is:

BSA = √[(Height × Weight) ÷ 3600]

Mosteller is attractive because it is easy to calculate and commonly used.

Du Bois has a much longer history.

Haycock provides another established alternative.

For many typical adult measurements, the results are reasonably close.

When a healthcare setting specifies a particular formula, use that formula rather than comparing numbers simply to choose the lowest or highest result.

Who Can Use This Tool?

A Body Surface Area Calculator can be useful for:

• Healthcare students learning clinical calculations

• Researchers studying body size normalization

• Patients trying to understand the meaning of BSA

• Professionals reviewing different BSA equations

• People learning how height and weight affect body size estimates

For educational purposes, the tool is convenient and easy to understand.

For clinical treatment, professional medical guidance should take priority.

When Should You Not Rely on an Online BSA Result?

An online Body Surface Area Calculator should not be the final authority when an important medical decision depends on the number.

Extra caution is appropriate when:

• A medication dose depends on BSA

• Chemotherapy treatment is involved

• A child or infant is being assessed

• The person’s body size is far outside typical ranges

• Height or weight is uncertain

• A hospital or treatment protocol specifies a particular formula

• The result is close to an important clinical decision threshold

NIDDK notes that people with unusually large or small body sizes, bodybuilders, frail older adults, people with amputations, and some other patients may have circumstances where standard creatinine based estimates require additional consideration.

Practical Tips for Better Results

Use recent height and weight measurements.

Check your units before calculating.

Keep the calculation date with the result if you are tracking BSA over time.

Use the same formula when comparing results from different dates.

Do not compare Du Bois, Mosteller, and Haycock values as though they were identical calculations.

Do not assume that additional decimal places mean additional clinical accuracy.

If a healthcare professional gives you a different BSA result, ask which formula was used.

Safety, Privacy, and Accuracy

The CalculatorKits Body Surface Area Calculator is intended for general educational use.

The calculator performs a mathematical estimate based on your entered height and weight.

The result cannot determine whether a particular BSA is appropriate for medication dosing, treatment, or another medical decision.

The CalculatorKits interface also states that calculations are performed locally in the browser and that no account is required.

For medical decisions, use the calculation provided or confirmed by your healthcare professional.

Frequently Asked Questions

What is a Body Surface Area Calculator?

A Body Surface Area Calculator estimates the approximate external surface area of the human body from height and weight. The result is usually expressed in square meters.

How is BSA calculated?

CalculatorKits uses the Du Bois formula as its primary method:

BSA = 0.007184 × Weight⁰·⁴²⁵ × Height⁰·⁷²⁵

Weight is expressed in kilograms and height in centimeters.

What does BSA stand for?

BSA stands for Body Surface Area.

What is a normal BSA?

There is no single BSA value that is normal for everyone. Estimated BSA varies mainly according to height and weight.

Is BSA the same as BMI?

No. BMI measures body weight relative to height. BSA estimates the approximate external surface area of the body.

Which BSA formula is most accurate?

There is no single formula that is best for every situation. Du Bois, Mosteller, and Haycock are established methods, and a clinical setting may specify which one should be used.

What formula does CalculatorKits use?

CalculatorKits uses the Du Bois equation as its primary BSA formula and provides comparison values using other established methods.

Why does my BSA differ from another website?

Different calculators may use different formulas, unit conversions, or rounding methods. Check the equation before comparing the results.

Is BSA used for medication dosing?

Yes. Some medications and treatment protocols use BSA based dosing. However, an online result should never be used by itself to determine an actual medication dose.

Is BSA used for chemotherapy?

Yes. Some chemotherapy protocols use BSA in their dosing calculations. The actual dose must be determined by the oncology team using the appropriate treatment protocol.

Is BSA used for kidney function?

Yes. BSA is relevant to the standardized reporting of eGFR and can also be important when adjusting kidney function for individual body size.

Does BSA change when weight changes?

Yes. Because weight is one of the main inputs, a significant change in body weight generally changes the estimated BSA.

Is a Body Surface Area Calculator accurate for children?

A formula can produce a mathematical estimate, but children have different body proportions and may require methods appropriate to their age and clinical situation.

Can I use BSA to calculate my own medicine dose?

No. Do not use an online BSA calculator to start, stop, or change medication.

Why do Du Bois and Mosteller give different results?

They use different mathematical formulas. Small differences are expected.

Key Takeaways

A Body Surface Area Calculator estimates the approximate external surface area of the body from height and weight.

The CalculatorKits tool uses the Du Bois formula as its primary method.

The Du Bois equation is:

BSA = 0.007184 × Weight⁰·⁴²⁵ × Height⁰·⁷²⁵

The result is expressed in square meters.

Mosteller and Haycock are other established BSA formulas and may provide slightly different results.

BSA is used in some medication dosing protocols, cardiac calculations, kidney function interpretation, and scientific research.

BSA is an estimate, not a direct physical measurement.

Height, weight, body proportions, and formula selection can affect the result.

Mathematical precision does not mean that the actual biological surface area is known to the same precision.

Never use an online BSA result by itself to determine a medication dose or medical treatment.

For clinical decisions, follow the formula and instructions provided by the appropriate healthcare professional.

Related CalculatorKits Tools

GFR Calculator
Estimate glomerular filtration rate using laboratory and personal information. This is useful when you are reviewing kidney function and want to understand how GFR relates to body surface area.

BMI Calculator
Calculate BMI from height and weight and review the standard BMI categories. BMI and BSA use similar measurements but have different purposes.

Ideal Weight Calculator
Compare height with several traditional ideal weight formulas. This provides another perspective on body size.

Body Type Calculator
Explore a general body structure classification using measurements such as height, weight, and wrist circumference.

References

1. Du Bois D and Du Bois EF, A Formula to Estimate the Approximate Surface Area if Height and Weight Be Known
   Historical research associated with the development of the Du Bois body surface area equation.
   PubMed: Du Bois and Du Bois Formula
2. Mosteller RD, Simplified Calculation of Body Surface Area
   Research describing the simplified Mosteller equation.
   PubMed: Mosteller Formula
3. Haycock GB, Schwartz GJ, and Wisotsky DH, Geometric Method for Measuring Body Surface Area
   Research describing the Haycock equation across infants, children, and adults.
   PubMed: Haycock Formula
4. Estimating Body Surface Area From Mass and Height: Theory and the Formula of Du Bois and Du Bois
   Later analysis examining the mathematical basis and practical use of the Du Bois approach.
   PubMed: Body Surface Area From Mass and Height
5. NIDDK, Determining Drug Dosing in Adults With Chronic Kidney Disease
   Explains the role of BSA in kidney function interpretation and the distinction between indexed kidney function and drug dosing considerations.
   NIDDK: Drug Dosing in CKD
6. NIDDK, Clinical Measurements and eGFR Accuracy
   Explains factors that can affect eGFR estimation and situations where body size may require additional consideration.
   NIDDK: Clinical Measurements and eGFR Accuracy
7. American Society of Clinical Oncology, Chemotherapy Dosing and Body Surface Area
   Provides clinical context for BSA based chemotherapy dosing and the use of standard BSA formulas.
   ASCO Guidance on Chemotherapy Dosing
8. CalculatorKits Body Surface Area Calculator
   Provides the CalculatorKits primary formula, calculator inputs, comparison methods, examples, and educational information.
   CalculatorKits: Body Surface Area Calculator

Medical Disclaimer

This article and the CalculatorKits Body Surface Area Calculator are provided for general educational and informational purposes only. The result is an estimate and is not a medical diagnosis, treatment recommendation, or substitute for professional medical judgment. BSA may be used as part of some clinical calculations, including certain medication dosing protocols, but medication doses must always be determined using the appropriate clinical protocol and qualified healthcare guidance. Do not use this calculator to start, stop, or change medication or treatment.

Written and reviewed by the CalculatorKits Editorial Team

Last Updated: September 6, 2026