About the Body Surface Area Calculator
Body Surface Area Calculator helps estimate the key numbers involved in other decisions. It is designed for quick scenario comparison: enter a realistic set of values, calculate the result, then change one assumption at a time to see what has the greatest effect. Unlike a static table, the result responds to your inputs and keeps the calculation in your browser. Health and fitness results are population-based estimates. They can support a conversation or planning process, but they do not determine an individual diagnosis, treatment, or safe activity level.
How to use this calculator
Enter values that match your situation and select Calculate result. Review the main result and its supporting figures, then change one input at a time to compare scenarios. Results are rounded for readability while the calculation retains additional precision internally.
Information you will need
- Weight
- Height
How the calculation works
Body surface area using Mosteller and Du Bois equations. Read the primary result together with the supporting values rather than focusing on one number alone. A useful estimate should make its assumptions visible. If the answer looks surprising, verify the unit, rate, time period, and whether the entered value is gross or net. Run a conservative and an optimistic scenario to understand the range of possible outcomes.
Formula or method
Mosteller: sqrt(H × W / 3600).
Worked example
70kg, 175cm = 1.85 m2.
The example is illustrative rather than a recommendation. Use your own verified values and keep all monetary or measurement units consistent. When comparing alternatives, save or note each result so the assumptions do not become mixed.
How to interpret the result
The primary output answers the main question posed by the body surface area calculator, while the additional cards provide context. A result with many decimal places is not necessarily more certain. The displayed precision makes comparison easier, but uncertainty in the inputs can be larger than the rounding difference.
Look for trends and ranges instead of treating a single estimate as a pass or fail result. If the output conflicts with symptoms, professional advice, or a direct measurement, rely on appropriate professional assessment.
Limitations and important notes
The body surface area calculator cannot account for every factor that affects an individual result. Measurement technique, hydration, body composition, medication, pregnancy, illness, training status, and normal biological variation may matter. Do not use an estimate to diagnose a condition, select medication dosage, decide whether to drive, or ignore symptoms. A qualified professional can interpret measurements in the context of history and appropriate testing.
Frequently asked questions
What is body surface area (BSA)?
Body surface area is the total surface area of your body, expressed in square meters. It is calculated from height and weight using formulas such as Mosteller or Du Bois. Average adult BSA is about 1.7-1.9 m². Clinically, BSA serves as an indicator of metabolic mass and has traditionally been used for medication dosing, especially in chemotherapy. BSA is an estimate intended for educational and clinical context, and dosing decisions always belong to your healthcare team.
How is BSA calculated?
The Mosteller formula is BSA = the square root of (height in cm times weight in kg divided by 3600). The Du Bois formula is BSA = 0.007184 x height^0.725 x weight^0.425. Both produce very similar results for typical adults, usually within 1-2% of each other. This calculator shows both for comparison. These formulas estimate surface area from two simple measurements and are validated for most adults, though they are less accurate at extremes of body composition.
What is the average BSA for an adult?
Average adult BSA is roughly 1.7 m², about 1.9 m² for men and 1.6-1.7 m² for women, with most adults falling between about 1.4 and 2.2 m². A 70 kg, 170 cm person is roughly 1.82 m². Interestingly, the 1.73 m² figure used to index GFR and other measurements comes from a 1927 average rather than a modern one, so today's averages are somewhat higher. Your personal value depends on your height and weight.
Why is BSA used for medication dosing?
Many drugs, especially chemotherapy agents, are dosed in mg per square meter because BSA correlates with cardiac output, organ size, and drug clearance better than body weight alone for many medications. A drug at 100 mg/m² for someone with a BSA of 1.82 m² would be about 182 mg. This standardizes drug exposure across different body sizes. However, BSA-based dosing has known limitations, and many newer agents now use flat or weight-based dosing instead. Follow your care team's protocol.
Which BSA formula should I use: Mosteller or Du Bois?
Both are widely used and nearly identical for most adults. Mosteller is simpler and commonly recommended in modern practice, while Du Bois is the historical standard still used in many references. For children, the Haycock formula is often preferred, and Boyd performs better at very low weights. If your clinic specifies a formula, match it; otherwise Mosteller is a fine default. Consistency between measurements over time matters more than the choice of formula.
Is BSA the same as BMI?
No. BMI, or body mass index, is weight divided by height squared and is used to classify weight status. BSA estimates total body surface area from height and weight using different mathematics. A person can have a normal BMI but a different BSA based on height, and vice versa. BSA is used for drug dosing and physiological indexing, while BMI is used for weight categories. They are complementary rather than interchangeable, and one calculator does not substitute for the other.
When is BSA used in medicine besides drug dosing?
BSA is used to index physiological values, such as the cardiac index, which is cardiac output divided by BSA with a normal range of about 2.5-4.0 L/min/m², and eGFR, which is reported per 1.73 m² to standardize kidney function across body sizes. It also helps estimate the percentage of skin burned using the Rule of Nines for fluid resuscitation in burn care, and it guides some pediatric dosing. In research, indexing measurements by BSA lets clinicians compare people of very different sizes fairly.