Body surface area, commonly abbreviated as BSA, is an estimate of the total external surface area of the human body. It is expressed in square meters (m²) and is widely used in medical calculations, clinical research, and healthcare settings.
BSA DuBois Calculator
The BSA DuBois Calculator provides a simple way to estimate body surface area using two basic measurements: height and weight. It uses the classic DuBois and DuBois formula, one of the earliest and still widely recognized equations for estimating BSA.
Unlike body mass index (BMI), which relates body weight to height, BSA is a measure of estimated body surface area. BSA calculations can be useful in certain clinical contexts because some physiological measurements and medication-related calculations are expressed relative to body surface area.
This calculator accepts height in either centimeters or inches and weight in either kilograms or pounds. If you enter US customary units, the calculator converts them to centimeters and kilograms before applying the DuBois equation. The result is displayed in square meters.
For example, a person who is 170 cm tall and weighs 70 kg has an estimated BSA of approximately 1.82 m² using the DuBois formula.
This guide explains what BSA means, how the DuBois formula works, how to use the calculator, how to perform the calculation manually, and what factors can affect the result.
What Is Body Surface Area (BSA)?
Body surface area represents an estimated measurement of the surface area of the human body. Because the human body has a complex shape, BSA cannot normally be measured simply with a ruler. Instead, mathematical formulas use variables such as height and weight to estimate it.
The result is expressed in:
m² (square meters)
For example:
- 1.50 m²
- 1.75 m²
- 2.00 m²
BSA is different from body weight and BMI. A person's weight tells you how much they weigh, while height describes their vertical measurement. BMI combines height and weight into a weight-status index. BSA instead estimates the body's external surface area from height and weight.
Several equations have been developed to estimate BSA. The DuBois and DuBois formula is one of the most historically established methods.
What Is the DuBois BSA Formula?
The DuBois and DuBois formula estimates body surface area using height in centimeters and weight in kilograms.
The formula is:
BSA = 0.007184 × Height⁰·⁷²⁵ × Weight⁰·⁴²⁵
Where:
- BSA = body surface area in m²
- Height = height in centimeters
- Weight = body weight in kilograms
- 0.007184 = constant used in the DuBois equation
- 0.725 = height exponent
- 0.425 = weight exponent
The exponents mean that BSA does not increase in a simple linear fashion with height or weight. Instead, the formula applies fractional powers to each measurement.
The calculator performs these calculations automatically after converting the entered measurements into the required units.
Why Is BSA Measured in Square Meters?
Area is measured in square units. Since BSA represents an estimated surface area, its standard unit is square meters (m²).
For comparison:
- Length → meters (m)
- Area → square meters (m²)
- Volume → cubic meters (m³)
A BSA result of 1.80 m² does not mean that a person is 1.80 meters tall. It means the estimated surface area of the body is approximately 1.80 square meters.
This distinction is important when interpreting BSA results.
How to Use the BSA DuBois Calculator
The calculator requires only height and weight.
Step 1: Enter Your Height
Enter your height into the Height field.
You can select either:
- cm
- inches
For example:
Height = 170 cm
or:
Height = 66.93 inches
Step 2: Enter Your Weight
Enter your body weight into the Weight field.
The calculator supports:
- kg
- lb
For example:
Weight = 70 kg
or approximately:
Weight = 154.32 lb
Step 3: Select the Correct Units
Make sure the selected unit matches the number you entered.
For example, if you enter 170 and select cm, the calculator interprets the height as 170 centimeters.
If you enter 70 and select kg, the calculator interprets the weight as 70 kilograms.
Step 4: Click Calculate
Select the Calculate button to obtain the estimated BSA.
The calculator displays:
- Body Surface Area
- Formula used
- Height used in centimeters
- Weight used in kilograms
Step 5: Review the Result
The primary result is displayed in m².
For example:
Body Surface Area: 1.82 m²
The calculator also shows the standardized height and weight values used in the calculation, which makes it easier to verify unit conversions.
Height and Weight Unit Conversions
The DuBois equation requires height in centimeters and weight in kilograms. If you select inches or pounds, the calculator converts those measurements automatically.
Inches to Centimeters
The conversion is:
1 inch = 2.54 cm
Therefore:
Height in cm = Height in inches × 2.54
For example:
70 inches × 2.54 = 177.80 cm
Pounds to Kilograms
The calculator uses:
1 pound = 0.45359237 kg
Therefore:
Weight in kg = Weight in pounds × 0.45359237
For example:
154 lb × 0.45359237 ≈ 69.85 kg
After conversion, the DuBois formula uses the resulting centimeter and kilogram values.
DuBois BSA Calculation Example
Let's calculate BSA for an adult who is:
- Height = 170 cm
- Weight = 70 kg
The DuBois equation is:
BSA = 0.007184 × Height⁰·⁷²⁵ × Weight⁰·⁴²⁵
Substitute the values:
BSA = 0.007184 × 170⁰·⁷²⁵ × 70⁰·⁴²⁵
After calculating the fractional powers and multiplying the values:
BSA ≈ 1.82 m²
Therefore, the estimated body surface area is approximately:
1.82 m²
This is an estimate based specifically on the DuBois and DuBois equation.
Example Using Inches and Pounds
Suppose a person is:
- Height = 68 inches
- Weight = 160 pounds
First, convert height:
68 × 2.54 = 172.72 cm
Next, convert weight:
160 × 0.45359237 ≈ 72.57 kg
Now substitute the converted values into the DuBois formula:
BSA = 0.007184 × 172.72⁰·⁷²⁵ × 72.57⁰·⁴²⁵
The resulting BSA is approximately:
1.86 m²
The important point is that you do not have to perform these conversions manually when using the calculator. Simply enter the measurements and select the appropriate units.
BSA DuBois Reference Examples
The following table provides approximate examples calculated using the DuBois equation.
| Height | Weight | Approximate BSA |
|---|---|---|
| 150 cm | 50 kg | 1.47 m² |
| 160 cm | 60 kg | 1.63 m² |
| 165 cm | 65 kg | 1.71 m² |
| 170 cm | 70 kg | 1.82 m² |
| 175 cm | 75 kg | 1.90 m² |
| 180 cm | 80 kg | 1.99 m² |
| 185 cm | 90 kg | 2.11 m² |
| 190 cm | 100 kg | 2.26 m² |
These are examples for understanding how the formula behaves. Individual results should be calculated from the person's actual height and weight.
How Height Affects BSA
Height is one of the two variables in the DuBois formula.
The formula raises height to the power of 0.725:
Height⁰·⁷²⁵
This means that increasing height generally increases estimated BSA, but not in a simple one-to-one relationship.
For example, keeping weight constant, a taller person will generally have a larger estimated body surface area.
This makes intuitive sense because a larger body generally has more external surface area.
How Weight Affects BSA
Weight is also incorporated into the DuBois equation:
Weight⁰·⁴²⁵
As weight increases, estimated BSA generally increases as well. However, because the exponent is 0.425 rather than 1, the relationship is not directly proportional.
For example, doubling weight does not double BSA.
This fractional relationship is one of the mathematical characteristics of the DuBois equation.
BSA vs. BMI
BSA and BMI both use height and weight, but they answer different questions.
| Feature | BSA | BMI |
|---|---|---|
| Full name | Body Surface Area | Body Mass Index |
| Main purpose | Estimates body surface area | Relates weight to height |
| Typical unit | m² | kg/m² |
| Uses height | Yes | Yes |
| Uses weight | Yes | Yes |
| DuBois formula | Yes | No |
| Represents body surface area | Yes | No |
| Used in some clinical calculations | Yes | Yes |
BMI is commonly used as a general weight-to-height index, while BSA is an estimated physical surface-area measurement.
Neither measurement by itself provides a complete picture of someone's health.
Why Is BSA Important in Healthcare?
BSA has been used in various medical and clinical calculations. In some situations, healthcare professionals may use BSA-based values because certain physiological measurements or treatment protocols have historically been expressed relative to body surface area.
One well-known application is body-surface-area-based medication dosing for certain therapies. BSA may also appear in calculations involving physiological parameters such as cardiac index or kidney-related measurements.
However, BSA should not automatically be interpreted as a medication dose.
A BSA result from an online calculator is an estimate, and medical professionals may use different formulas, clinical protocols, patient-specific factors, or adjusted dosing methods depending on the situation.
If BSA is being used for medical treatment or medication dosing, always follow the instructions of the prescribing clinician or healthcare professional.
Different BSA Formulas
The DuBois equation is not the only formula available for estimating body surface area.
Other commonly known formulas include:
- Mosteller
- Haycock
- Gehan and George
- Boyd
- Fujimoto
Different equations can produce slightly different BSA values for the same height and weight.
For example, the Mosteller formula is often written as:
BSA = √[(Height(cm) × Weight(kg)) ÷ 3600]
The DuBois formula, however, uses fractional exponents:
BSA = 0.007184 × Height⁰·⁷²⁵ × Weight⁰·⁴²⁵
Therefore, when comparing BSA results, it is important to know which formula was used.
The calculator on this page specifically uses the DuBois & DuBois formula.
DuBois vs. Mosteller Formula
| Feature | DuBois & DuBois | Mosteller |
|---|---|---|
| Height required | cm | cm |
| Weight required | kg | kg |
| Result | m² | m² |
| Mathematical structure | Fractional powers | Square root |
| Common use | Established BSA estimation | Common clinical BSA estimation |
| Calculator on this page | Yes | No |
Neither formula should automatically be assumed to be the appropriate method for every clinical application. If a healthcare professional specifies a particular formula, use that formula.
What Does a BSA of 1.8 m² Mean?
A result of 1.8 m² means the DuBois formula estimates the person's body surface area at approximately 1.8 square meters.
It does not mean that the person has a "good" or "bad" BSA.
BSA varies with body size, including height and weight. Therefore, there is no single BSA value that should be considered ideal for everyone.
A BSA result should be interpreted in the context in which it is being used.
Factors That Can Affect the Calculated BSA
The calculator uses only two measurements:
- Height
- Weight
Consequently, the calculated result depends heavily on the accuracy of these measurements.
Accurate Height Measurement
Height should preferably be measured without shoes and using an appropriate measuring method.
Accurate Weight Measurement
Weight should be entered using the same units selected in the calculator.
Unit Selection
An incorrect unit can produce a dramatically incorrect result. For example, entering a weight of 70 and selecting pounds produces a completely different calculation from entering 70 kilograms.
Rounding
The calculator displays the BSA result to two decimal places. The internally calculated value may contain additional decimal places before being rounded for display.
Why the Calculator Shows Height Used and Weight Used
The calculator displays the converted values used in the calculation.
For example, if you enter:
Height = 70 inches
the calculator converts this to:
177.80 cm
If you enter:
Weight = 160 lb
it converts the value to approximately:
72.57 kg
Showing these standardized values helps you check whether the selected units were correct.
It is particularly useful when working with measurements from different systems.
Common Mistakes When Calculating BSA
Entering the Wrong Height Unit
If you enter height in inches but leave the unit set to centimeters, the calculation will be incorrect.
Always verify the unit selector.
Entering Pounds as Kilograms
A weight of 150 pounds is not the same as 150 kilograms.
When using pounds, select lb.
Mixing Units
The calculator provides separate unit selectors for height and weight, so you can use centimeters with kilograms or inches with pounds.
However, the selected unit must match the actual number entered.
Using BSA as a Standalone Health Assessment
BSA is an estimate of surface area, not a complete measure of health, fitness, body composition, or nutritional status.
Assuming Every Clinical Calculation Uses DuBois
Different medical calculations can use different BSA formulas. If a professional or medical reference specifies another equation, follow that specific method.
Practical BSA Calculation Table
Here is another quick reference showing how BSA can vary with height and weight.
| Height | 60 kg | 70 kg | 80 kg | 90 kg |
|---|---|---|---|---|
| 160 cm | ~1.63 m² | ~1.74 m² | ~1.84 m² | ~1.94 m² |
| 170 cm | ~1.72 m² | ~1.82 m² | ~1.92 m² | ~2.02 m² |
| 180 cm | ~1.82 m² | ~1.92 m² | ~2.02 m² | ~2.12 m² |
| 190 cm | ~1.91 m² | ~2.01 m² | ~2.11 m² | ~2.21 m² |
The values are approximate and are intended for comparison and educational purposes. The calculator should be used with the actual measurements for a specific result.
Benefits of Using a BSA DuBois Calculator
A dedicated calculator can make BSA estimation faster and more convenient than performing the equation manually.
Quick Calculation
You only need height and weight.
Multiple Unit Options
Height can be entered in centimeters or inches, while weight can be entered in kilograms or pounds.
Automatic Conversion
The calculator converts US customary measurements into the metric units required by the DuBois equation.
Clear Results
The BSA is presented in square meters, along with the formula and standardized input values.
Reduced Arithmetic Errors
Fractional exponents can be inconvenient to calculate manually. A calculator handles those operations automatically.
Is BSA the Same as Body Area?
BSA stands for body surface area, but it should not be confused with the area of a particular body part.
For example, BSA is not the surface area of your arm, leg, chest, or abdomen. It is an estimate of the overall external surface area of the body.
The DuBois formula estimates this value indirectly using height and weight.
When Should You Talk to a Healthcare Professional?
If you are using BSA for a medical purpose, especially medication dosing, treatment planning, or interpretation of a medical measurement, discuss the result with a qualified healthcare professional.
An online BSA calculator can perform the mathematical estimate, but it does not know a person's complete medical history, diagnosis, treatment plan, laboratory results, or other clinical factors.
For that reason, the calculator should be treated as a calculation and educational tool, not as a substitute for professional medical advice.
Frequently Asked Questions
1. What is the DuBois BSA formula?
The DuBois and DuBois formula is:
BSA = 0.007184 × Height⁰·⁷²⁵ × Weight⁰·⁴²⁵
Height is measured in centimeters, weight is measured in kilograms, and the result is expressed in square meters.
2. What does BSA stand for?
BSA stands for Body Surface Area. It is an estimate of the total external surface area of the human body and is normally expressed in square meters.
3. What units does the BSA DuBois Calculator use?
The calculator accepts height in centimeters or inches and weight in kilograms or pounds. It converts the measurements to centimeters and kilograms before applying the DuBois formula.
4. What is a normal BSA?
There is no single BSA value that is considered normal or ideal for every person. BSA varies according to body size, particularly height and weight.
5. How is BSA different from BMI?
BMI is a weight-to-height index expressed in kg/m², while BSA estimates the body's external surface area and is expressed in m². They use height and weight differently and serve different purposes.
6. Can BSA be used to calculate medication doses?
BSA is used in some medication-dosing protocols, but you should never determine or change a medication dose solely from an online BSA calculator. Follow the specific instructions of a qualified healthcare professional.
7. Can I calculate BSA using pounds and inches?
Yes. This calculator accepts pounds and inches. It automatically converts inches to centimeters and pounds to kilograms before applying the DuBois equation.
8. Why are different BSA calculators sometimes slightly different?
Different calculators may use different BSA equations, such as DuBois, Mosteller, Haycock, or other formulas. Because the mathematical equations differ, their results can vary slightly.
9. What is the BSA of a person who is 170 cm and 70 kg?
Using the DuBois and DuBois formula, a person who is 170 cm tall and weighs 70 kg has an estimated BSA of approximately 1.82 m².
10. Is the DuBois BSA Calculator medically accurate?
The calculator correctly applies the DuBois equation to the height and weight entered, but BSA itself is an estimate rather than a direct measurement of actual body surface area. For medical decisions, use the formula and interpretation specified by your healthcare professional.
Final Thoughts
The BSA DuBois Calculator provides a straightforward way to estimate body surface area from height and weight. By using the established DuBois and DuBois equation, the tool converts measurements into the units required for the formula and returns the estimated result in square meters.
To use it, enter your height and choose either centimeters or inches. Then enter your weight and select kilograms or pounds. After calculating, the tool displays your estimated BSA along with the standardized height and weight values used in the equation.
The underlying formula is:
BSA = 0.007184 × Height⁰·⁷²⁵ × Weight⁰·⁴²⁵
Accurate measurements and correct unit selection are important because both height and weight directly affect the result. It is also important to remember that the DuBois equation is only one of several established BSA formulas, so different calculators may produce slightly different results.
BSA can be useful in certain clinical and scientific contexts, but it should not be interpreted as a general measure of health or used independently to make medical decisions. If you need BSA for medication dosing, treatment planning, or another healthcare purpose, use the method specified by your healthcare professional.
For quick educational calculations and general reference, however, the BSA DuBois Calculator offers a convenient way to estimate body surface area using either metric or US customary height and weight measurements.
:::