Introduction
Body Surface Area (BSA) is a measurement of the total area of skin that covers your body. Doctors and nurses use BSA to figure out the right dose of medicine, especially for treatments like chemotherapy. It is also helpful for checking kidney function and heart health. Unlike body weight alone, BSA takes both your height and weight into account.
This BSA Calculator makes it quick and easy to find your body surface area. Simply enter your height and weight, and the tool returns your result. It uses trusted formulas that doctors rely on every day. This calculator gives you a fast and reliable result.
How to Use Our BSA Calculator
Enter your height and weight below to quickly calculate your body surface area (BSA). The calculator will give you your BSA result in square meters (m²).
Height: Type in your height using either centimeters or inches. This is how tall you are from head to toe. You can measure your height by standing straight against a wall.
Weight: Type in your body weight using either kilograms or pounds. For the best result, use a digital scale on a hard floor and remove your shoes and heavy clothing. You can also use our Ideal Body Weight Calculator to see how your current weight compares to recommended ranges.
Age: Pick 20 or older, or Under 20. For anyone under 20, the results show BMI without the adult BMI category, ideal weight range, BMI Prime, or target weight, since the adult BMI categories are for adults 20 and older.6
Formulas: You do not need to pick one. The results show all eight formulas side by side. The most common ones are the Du Bois formula and the Mosteller formula. If your result will be used for a treatment, use the formula your care team uses. A validated formula should be chosen and used every time to avoid mix-ups.1
Once you enter your numbers and click calculate, the tool will show your body surface area in square meters. BSA is used by doctors to figure out the right dose of certain medicines, especially chemotherapy drugs. It is also helpful for understanding your body size in a way that accounts for both height and weight.
What Is Body Surface Area (BSA)?
Body Surface Area, or BSA, is a measure of the total outer area of your body, expressed in square meters (m²). Doctors and nurses use BSA to make important medical decisions, such as figuring out the right dose of certain drugs (especially chemotherapy), estimating kidney function, working out the cardiac index, and assessing burn injuries.1 Unlike body weight alone, BSA accounts for both your height and weight together.
How Is BSA Calculated?
Measuring BSA directly takes many detailed body measurements, so scientists have developed mathematical formulas to estimate it.2 The most common formula is the Du Bois & Du Bois formula,4 developed by Eugene and Delafield Du Bois, which uses your weight and height in a specific equation and remains widely used today.1 Other well-known formulas include Mosteller (a simpler formula that is widely used) and Haycock, both designed with children in mind,1 and Gehan & George. Each formula uses slightly different math. The formulas agree most closely for people of middle weight who are on the tall side.4 Across 25 published formulas, results for a standard adult build can differ by up to 0.5 m², and the gaps grow at short heights, which is a concern for short, heavy adults and for children.4
Why Are There So Many BSA Formulas?
Different formulas were developed over the years to better fit certain groups of people. For example, the Fujimoto and Takahira formulas were designed using data from Japanese and East Asian populations. The Fujimoto formula used here is the one its authors gave for ages 6 and older.5 The Schlich formula accounts for differences between males and females. The Boyd formula is a classic equation that uses a more complex calculation. The formulas can give quite different results, and that matters most when dosing powerful medications.1 Your doctor will choose the formula that best fits your situation.
What Is a Normal BSA?
BSA rises with height and weight, so adults have larger values than children, and men on average larger values than women because they are generally taller and heavier. Your BSA naturally changes as you grow, gain weight, or lose weight. To understand your body composition in more detail, you might also explore our Lean Body Weight Calculator.
BSA vs. BMI: What's the Difference?
BSA measures your body's total surface area and is mainly used in clinical and medical settings. BMI (Body Mass Index) is a ratio of your weight to your height squared, and it is used to classify whether a person is underweight, normal weight, overweight, or obese. This calculator provides both values so you can see a complete picture of your body metrics. A healthy BMI range for most adults is 18.5 to 24.9 kg/m².3 For children and teens aged 2 through 19, BMI is read against BMI-for-age percentiles for their sex, not the adult categories.6
Why Does BSA Matter in Medicine?
- Drug dosing: Many chemotherapy drugs and some antibiotics are dosed based on BSA rather than body weight to reduce the risk of giving too much or too little medication.
- Kidney function: Glomerular filtration rate (GFR), which measures how well your kidneys filter blood, is often adjusted to BSA.
- Cardiac index: Heart performance can be measured per unit of BSA, giving doctors a standardized way to compare heart function across patients of different sizes.
- Burn assessment: The percentage of BSA affected by burns helps medical teams decide on fluid replacement and treatment plans.
Understanding your BSA is just one part of a complete health picture.
Important: This BSA calculator is meant for educational purposes only. It should not replace advice from a doctor, pharmacist, or other qualified healthcare professional. Always consult your medical provider before making any health or treatment decisions based on these results.