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- Body surface area (BSA) is the total area of the outside of the body, measured in square meters (m²).
- It is worked out from height and weight. The Mosteller formula is the most widely used: BSA = √(height in cm × weight in kg ÷ 3,600).
- An adult who is 170 cm tall and weighs 70 kg has a BSA of about 1.82 m².
- BSA is used in medicine, for example for some drug doses. Never change a dose based on a calculator.
How to use the body surface area calculator
Choose units
Pick metric (centimeters and kilograms) or US units (feet, inches and pounds).
Enter height
Use a measured height without shoes.
Enter weight
Use a recent weight.
Read your BSA
You get the Mosteller result plus the Du Bois, Haycock and Gehan-George results, and the steps used.
BSA formulas
Body surface area formulas (height in cm, weight in kg)
Mosteller: BSA = √(height × weight ÷ 3,600)
Du Bois and Du Bois: BSA = 0.007184 × height0.725 × weight0.425
Haycock: BSA = 0.024265 × height0.3964 × weight0.5378
Gehan and George: BSA = 0.0235 × height0.42246 × weight0.51456
All four give the result in square meters. Mosteller is the easiest to work out by hand.
How to calculate BSA by hand
Multiply height by weight
170 cm × 70 kg = 11,900.
Divide by 3,600
11,900 ÷ 3,600 = 3.306.
Take the square root
√3.306 = 1.82.
Add the unit
The BSA is 1.82 m², about 19.6 square feet.
BSA chart by height and weight
Mosteller and Du Bois results
Body surface area in m² for some common sizes.
- 150 cm, 50 kg 1.44 / 1.43
- 160 cm, 60 kg 1.63 / 1.62
- 170 cm, 70 kg 1.82 / 1.81
- 180 cm, 80 kg 2.00 / 2.00
- 190 cm, 90 kg 2.18 / 2.18
- Child: 110 cm, 19 kg 0.76 / 0.76
For adults of ordinary size the formulas agree closely. Differences are larger for very small children and people with obesity.
What BSA is used for
Doctors and pharmacists use BSA to scale some medicines, most often chemotherapy, because it tracks body size and metabolism better than weight alone for certain drugs. It is also used to index heart measurements such as cardiac output, and kidney function results are often expressed per 1.73 m², a standard adult body surface area.
A calculator result is for information only. Medicine doses are always set and checked by your care team, who may use a specific formula or adjust for your situation.
Where a BSA calculator helps
Students and nurses
Check BSA arithmetic quickly and see the steps.
Understanding a report
See what a BSA figure on a medical note means.
Comparing formulas
See how Mosteller, Du Bois, Haycock and Gehan-George differ.
Children
Haycock and Mosteller are often used for children.
See your BMI, your basal metabolic rate or a child’s BMI percentile. This page is general information, not medical advice.
Body surface area calculator FAQ
What is a normal body surface area?
It depends on size. Many adults fall between about 1.6 and 2.0 m², and 1.73 m² is used as a standard adult value in kidney function tests.
Which BSA formula is most accurate?
None is perfect. Mosteller is the most widely used and simple, Du Bois is the oldest, and Haycock is often used for children. They agree closely for most adults.
How do I calculate BSA with the Mosteller formula?
Multiply height in cm by weight in kg, divide by 3,600 and take the square root. For 170 cm and 70 kg that is 1.82 m².
Can I use pounds and inches?
Yes. Choose US units and the calculator converts them to centimeters and kilograms first.
Why is BSA used for drug doses?
For some drugs, especially in cancer care, body surface area matches how the body handles the drug better than weight alone. Your care team sets and checks every dose.