This BSA BMI calculator gives two numbers from your height and weight: body surface area (BSA) in square metres and body mass index. BSA estimates the total area of your skin. Doctors use it, rather than weight alone, to dose some medicines and to compare heart and kidney measurements between people of different sizes.
The calculator shows BSA by the Mosteller formula, the one most used in clinics, and by the older Du Bois formula for comparison. BMI appears alongside, labelled by Indian and WHO bands.
Quick numbers
Mosteller
√(height cm × weight kg ÷ 3600)Du Bois
0.007184 × kg^0.425 × cm^0.725Typical adult woman
about 1.5 to 1.7 m²Typical adult man
about 1.7 to 2.0 m²Used for
medicine doses, cardiac index, kidney function
BSA BMI calculator formulas
BSA (Mosteller) = √(height in cm × weight in kg ÷ 3600)
BSA (Du Bois) = 0.007184 × weight^0.425 × height^0.725
BMI = weight in kg ÷ (height in m)²
A woman of 160 cm and 58 kg: Mosteller BSA = √(160 × 58 ÷ 3600) = 1.61 m². Her BMI is 22.7.
BSA and BMI at common sizes
| Height, weight | BSA Mosteller (m²) | BSA Du Bois (m²) | BMI |
|---|---|---|---|
| 150 cm, 45 kg | 1.37 | 1.37 | 20.0 |
| 155 cm, 52 kg | 1.50 | 1.49 | 21.6 |
| 160 cm, 58 kg | 1.61 | 1.60 | 22.7 |
| 165 cm, 65 kg | 1.73 | 1.72 | 23.9 |
| 170 cm, 70 kg | 1.82 | 1.81 | 24.2 |
| 175 cm, 78 kg | 1.95 | 1.94 | 25.5 |
| 180 cm, 85 kg | 2.06 | 2.05 | 26.2 |
The two BSA formulas usually agree within 0.02 to 0.05 m² for average adults. They drift apart more for very large or very small people.
Why doctors use body surface area
- Cancer medicines: many chemotherapy doses are written per square metre of BSA.
- Heart: cardiac output divided by BSA gives the cardiac index, so hearts of different body sizes can be compared.
- Kidneys: kidney filtration rates are often adjusted to a standard 1.73 m² surface.
- Children: some paediatric doses use BSA because it tracks metabolism better than weight in growing bodies.
BSA is a clinical tool. Do not use it to change any medicine dose yourself.
BSA vs BMI
BMI asks whether weight suits height; BSA asks how big the body is overall. Two people sharing one BMI can have very different BSA if one is tall and the other short. For personal health goals, BMI with waist size is more useful; see the BMI calculator and the BMI chart.
Getting accurate inputs
Small measuring errors matter for dosing. Clinics measure height without shoes and weight on a calibrated scale on the day of treatment. At home, the same care makes the number more reliable.
If you are being treated with medicines dosed by BSA, your doctor and pharmacist will measure and calculate it. Ask them if you have questions about your dose.
Frequently asked questions
What is a BSA BMI calculator?
A tool that works out body surface area and body mass index from the same height and weight.
What is a normal BSA for an adult?
About 1.5 to 1.7 m² for many women and 1.7 to 2.0 m² for many men. The commonly used average is 1.73 m².
Which BSA formula is best?
Mosteller is the most widely used because it is simple and accurate for most adults. Du Bois is older and gives similar results.
How is BSA used in medicine?
To dose some drugs, especially chemotherapy, and to adjust heart and kidney measurements for body size.
Is BSA the same as BMI?
No. BMI compares weight with height; BSA estimates the total surface area of the body.
How do I calculate BSA by hand?
Multiply height in cm by weight in kg, divide by 3600 and take the square root.
Sources
- Mosteller body surface area formula
- Du Bois body surface area formula