body Surface Area Calculato

Enter your height and weight, choose your preferred units, and calculate your estimated body surface area in seconds.

Important: BSA is an estimated measurement. It should not be used by itself to change medication doses or make medical decisions. If you are using BSA for treatment or medication, follow the calculation method and instructions provided by your healthcare professional.

What Is Body Surface Area?

Body Surface Area (BSA) is an estimate of the total external surface area of the human body.

BSA is normally expressed in square meters (m²).

Unlike BMI, which compares weight with height squared, BSA estimates the body’s external surface area using measurements such as height and weight.

BSA is commonly used in medical and scientific settings, including some drug-dosing calculations and measurements that are adjusted for body size. Different formulas can give slightly different results.

What Is a BSA Calculator?

A BSA calculator is an online tool that estimates body surface area using your height and weight.

Most calculators allow you to enter:

• Height in centimeters
• Weight in kilograms
• Height in feet and inches
• Weight in pounds

The calculator then converts the measurements when necessary and applies a BSA formula.

The Mosteller formula is commonly used because it is simple and easy to calculate. Other commonly referenced formulas include Du Bois, Haycock, and Gehan & George.

How to Use the Body Surface Area Calculator

Using the calculator is easy.

Step 1: Enter your height

Enter your height in either:

• Centimeters (cm), or
• Feet and inches

Step 2: Enter your weight

Enter your weight in:

• Kilograms (kg), or
• Pounds (lb)

Step 3: Select the formula

If the calculator gives you a choice, you can select a BSA formula such as Mosteller.

Step 4: Calculate your BSA

Click the calculate button.

Your estimated body surface area will be displayed in m².

For example, a person who is 170 cm tall and weighs 70 kg has a BSA of about 1.82 m² using the Mosteller formula.

Body Surface Area Formula

There are several formulas for estimating BSA.

The most commonly recognized formulas include:

• Mosteller
• Du Bois and Du Bois
• Haycock
• Gehan and George
• Boyd

The formulas were developed using different data sets and methods, so their results may differ slightly.

Mosteller Formula

The Mosteller formula is one of the simplest BSA formulas.

Mosteller BSA formula

BSA = √[(Height × Weight) ÷ 3600]

Height must be in centimeters and weight must be in kilograms.

For example:

Height = 170 cm

Weight = 70 kg

BSA:

√[(170 × 70) ÷ 3600]

= √3.3056

= 1.82 m²

The simplicity of this formula is one reason it is widely used.

Du Bois Formula

The Du Bois and Du Bois formula is an older and well-known BSA equation.

Du Bois BSA formula

BSA = 0.007184 × Height⁰·⁷²⁵ × Weight⁰·⁴²⁵

Height is measured in centimeters and weight in kilograms.

This formula remains an important reference when discussing body surface area calculations.

Haycock Formula

The Haycock formula is another commonly used BSA equation.

Haycock BSA formula

BSA = 0.024265 × Height⁰·³⁹⁶⁴ × Weight⁰·⁵³⁷⁸

The Haycock formula has been used across pediatric and adult populations and is often included when comparing BSA estimates.

Gehan and George Formula

The Gehan and George formula is another method for estimating body surface area.

Gehan and George formula

BSA = 0.0235 × Height⁰·⁴²²⁴⁶ × Weight⁰·⁵¹⁴⁵⁶

As with other BSA equations, height is in centimeters and weight is in kilograms.

BSA Calculator Example

Let’s calculate BSA for a person with:

Height: 170 cm

Weight: 70 kg

Using the Mosteller formula:

BSA = √[(170 × 70) ÷ 3600]

First multiply height and weight:

170 × 70 = 11,900

Then divide by 3,600:

11,900 ÷ 3,600 = 3.3056

Now take the square root:

√3.3056 = 1.818

Rounded to two decimal places:

BSA = 1.82 m²

This is an estimated value, not a direct measurement of the person’s actual skin surface.

BSA in Square Meters

BSA is commonly reported in square meters (m²).

For example:

BSA = 1.82 m²

The unit m² means square meters.

Some calculators may also provide the result in square feet (ft²).

Because different BSA formulas can produce slightly different results, it is important to use the same formula when comparing repeated calculations.

BSA Calculator in cm and kg

The easiest way to use most BSA formulas is to enter:

Height = cm

Weight = kg

For example:

Height: 175 cm

Weight: 75 kg

The calculator converts these values into the required format and calculates BSA.

The Mosteller formula is:

BSA = √[(175 × 75) ÷ 3600]

The result is approximately:

1.89 m²

BSA Calculator in Feet, Inches, and Pounds

If you use US or imperial measurements, you may have:

• Height in feet
• Height in inches
• Weight in pounds

For example:

Height = 5 ft 9 in

Weight = 160 lb

A calculator can convert these measurements into centimeters and kilograms before applying the BSA formula.

This makes it easier to calculate BSA without doing the unit conversion yourself.

Why Is Body Surface Area Used?

Body surface area is useful because body size cannot always be described well by weight alone.

In some medical calculations, a value may be expressed per square meter of body surface area.

BSA is used in areas such as:

• Some medication calculations
• Some chemotherapy protocols
• Cardiac index
• Certain physiological measurements
• Research and clinical calculations

However, the appropriate formula and calculation method depend on the specific medical situation. BSA should not be used on its own to decide or change a medication dose.

BSA and Medication Dosing

You may see medication information expressed as mg/m².

In simple mathematical terms:

Dose = Dose per m² × BSA

For example, if a clinical protocol specifies a dose based on body surface area, the patient’s BSA may be part of the calculation.

However, this does not mean you should use an online BSA calculator to choose or change a real medication dose.

Drug dosing can depend on many other factors, including the medication, condition being treated, age, kidney and liver function, treatment protocol, and clinical judgment.

Always follow the dose calculated and verified by your healthcare professional.

BSA vs BMI

BSA and BMI are not the same thing.

BMI

BMI uses height and weight to estimate weight status.

The BMI formula is:

BMI = Weight ÷ Height²

BSA

BSA estimates total body surface area using height and weight.

BSA is usually expressed in:

m²

BMI is expressed as a numerical index, while BSA is an estimated surface area.

So, a BSA calculator should not be used as a replacement for a BMI calculator.

BSA vs Body Weight

Body weight tells you how much a person weighs.

BSA estimates the external surface area of the body.

Two people can have the same weight but different heights and body proportions, so their estimated BSA may be different.

This is one reason height is included in common BSA formulas.

Mosteller vs Du Bois Formula

The Mosteller and Du Bois formulas are two commonly referenced methods for estimating BSA.

Feature	Mosteller	Du Bois
Formula type	Square-root formula	Power formula
Height	cm	cm
Weight	kg	kg
Result	m²	m²
Main advantage	Simple calculation	Historical reference
Commonly used	Yes	Yes

For ordinary adult measurements, commonly used formulas often give similar but not identical estimates.

Why Do Different BSA Calculators Give Different Answers?

You may notice that two BSA calculators give slightly different results.

This does not automatically mean one calculator is wrong.

The reason is that different calculators may use different formulas.

For example, one calculator may use:

Mosteller

while another may use:

Du Bois

or:

Haycock

The equations are different, so the final result can vary slightly.

For repeated calculations, it is helpful to use the same formula and units each time.

BSA for Children

BSA can also be estimated for children, but children’s body proportions change as they grow.

Some BSA formulas have been evaluated across pediatric populations, including the Haycock formula.

For medical treatment or pediatric medication dosing, use the method specified by the child’s healthcare professional rather than choosing a formula yourself.

BSA for Adults

For adults, BSA can be estimated from height and weight using formulas such as Mosteller, Du Bois, Haycock, or Gehan & George.

The Mosteller formula is particularly convenient because it uses a simple square-root calculation.

What Is a Normal Body Surface Area?

There is no single BSA value that is “normal” for every person.

BSA depends on factors such as:

• Height
• Weight
• Age
• Body size
• The formula used

Some references use approximately 1.73 m² as a reference adult BSA, but this is a reference value and should not be treated as a target or ideal BSA for an individual.

How Accurate Is a BSA Calculator?

A BSA calculator provides an estimate, not a direct measurement.

Different equations were developed from different groups of people and measurement methods. As a result, formulas can produce slightly different answers.

For everyday educational calculations, the difference between common formulas may be small. At unusual body sizes, the formulas can differ more.

If BSA is being used for a medical decision, always use the formula and protocol recommended by the healthcare professional.

When Should You Use a BSA Calculator?

A BSA calculator can be useful when you want to:

• Learn how BSA is calculated
• Check a mathematical calculation
• Convert height and weight into a BSA estimate
• Compare common BSA formulas
• Understand medical or scientific calculations
• Study physiology or pharmacology
• Calculate BSA for an educational example

It is not intended to replace professional medical advice.

Frequently Asked Questions

What is a Body Surface Area Calculator?

A Body Surface Area Calculator estimates the surface area of the human body from height and weight. The result is generally given in square meters (m²).

What does BSA stand for?

BSA stands for Body Surface Area.

What is the Mosteller BSA formula?

The Mosteller formula is:

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

What information do I need to calculate BSA?

Most common BSA calculators require only two measurements:

Height and weight.

What unit is BSA measured in?

BSA is normally measured in square meters (m²).

Some calculators may also show the result in square feet.

What is the average BSA?

There is no single BSA that applies to everyone. Some medical references use 1.73 m² as a reference adult value, but it is not an ideal or target value for every person.

Is BSA the same as BMI?

No. BMI and BSA are different measurements.

BMI uses height and weight to calculate a weight-related index, while BSA estimates the external surface area of the body.

Which BSA formula is best?

There is no single formula that is best for every situation. Mosteller is popular because it is simple, while other formulas such as Du Bois, Haycock, and Gehan & George may also be used depending on the context.

Why does my BSA result change with different calculators?

Different calculators may use different BSA formulas. Because the equations are different, the results may vary slightly.

Can BSA be calculated using feet and pounds?

Yes. If your calculator supports imperial units, you can enter height in feet and inches and weight in pounds. The calculator can convert them before calculating BSA.

Can I calculate BSA without a calculator?

Yes. You can use the Mosteller formula manually:

BSA = √[(Height × Weight) ÷ 3600]

Remember that height must be in centimeters and weight must be in kilograms.

Is a BSA calculator safe for medical dosing?

A BSA calculator can provide a mathematical estimate, but you should not use it alone to choose or change a medication dose. Follow the instructions of your doctor or pharmacist.

Final Thoughts

A Body Surface Area Calculator is a quick way to estimate BSA from your height and weight.

The Mosteller formula is one of the simplest methods:

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

You can also compare the result with other commonly used formulas, including Du Bois, Haycock, and Gehan & George.

Whether you are a student, teacher, researcher, or simply learning how BSA works, CalculatorGuides.com makes the calculation easy to understand.

For medical treatment, medication dosing, or chemotherapy calculations, always use the formula and instructions provided by your healthcare professional.