About the Body Surface Area Calculator
Body surface area, or BSA, is the total area of the outside of the body, measured in square metres. Doctors use it to scale some medicine doses, particularly chemotherapy, and to compare measurements such as cardiac output between people of different sizes. This body surface area calculator takes your height and weight, in metric or imperial units, and works out BSA with four published formulas: Mosteller, Du Bois, Haycock and Gehan and George. It shows each result side by side so you can see how closely they agree, and the average. The result is for information and is not a clinical dose calculation.
Updated October 2026
How to use the Body Surface Area Calculator
- 1Choose centimetres and kilograms, or inches and pounds.
- 2Enter your height.
- 3Enter your weight.
- 4Read the BSA in square metres from each formula.
- 5Use the formula that your doctor or reference requires.
The four formulas
- Mosteller: √(height cm × weight kg ÷ 3,600)
- Du Bois: 0.007184 × weight^0.425 × height^0.725
- Haycock: 0.024265 × weight^0.5378 × height^0.3964
- Gehan and George: 0.0235 × weight^0.51456 × height^0.42246
Reading the results
If the four answers differ by less than 0.05 square metres, which is typical for adults, it does not much matter which you pick. Larger gaps appear in children or very tall, short or heavy people. Pharmacists often cap BSA at a maximum value for dosing, so what is printed on a prescription may differ from the raw formula result.
Related health tools
The BMI Calculator, Ideal Weight Calculator and Body Fat Calculator describe weight and composition, the BMR Calculator estimates calories burned at rest and the Unit Converter moves between metric and imperial. This calculator is for education and general information, and it does not replace a doctor's advice or a pharmacist's dose calculation.
Features
- Mosteller, Du Bois, Haycock and Gehan-George formulas
- Metric and imperial units
- Average of the four results
- Result in square metres and square feet
- Checks for unlikely heights and weights
- Works for children and adults
- Runs in your browser
Frequently asked questions
What is the Mosteller formula?
Mosteller's formula is the square root of height in centimetres times weight in kilograms, divided by 3,600. It is the easiest to calculate by hand and is widely used in hospitals. A person 180 cm tall weighing 80 kg has a BSA of exactly 2.00 square metres.
What is a normal body surface area?
The average adult BSA is about 1.7 square metres, around 1.9 for men and 1.6 for women. Children have a smaller BSA, from about 0.25 at birth to around 1.0 at age 8 or 9. The value depends on height and weight rather than on health.
Why is BSA used for medicine doses?
Some drugs, especially in cancer treatment, are dosed per square metre because BSA relates better to metabolic rate and blood volume than weight alone. A doctor or pharmacist decides which formula and any adjustments to use, so never work out a dose from this tool.
Which formula is most accurate?
They agree within a few percent for most adults. Du Bois is the oldest and most cited, Mosteller is simple and popular, Haycock is often used for children, and Gehan and George was built from a large range of ages. For very small, very large or unusually shaped bodies the differences can grow.
Can I use it for babies and children?
The formulas work across sizes, but Haycock and Gehan and George were designed with children in mind. Heights and weights must be within the ranges of 30 to 250 cm and 2 to 400 kg. For any medical use, follow a paediatric specialist's guidance.
Is body surface area the same as BMI?
No. BMI is weight divided by height squared and describes weight status, while BSA estimates the skin area. They use similar inputs but answer different questions, and one does not predict the other.