How to use the body surface area calculator
- 1 Choose centimeters and kilograms or inches and pounds.
- 2 Enter height.
- 3 Enter weight.
- 4 Read the body surface area by each formula.
Worked example
An adult 170 cm tall weighing 70 kg. By Mosteller, BSA = √(170 × 70 ÷ 3600) = 1.818 m². Du Bois gives 1.810, Haycock 1.826, Gehan-George 1.831 and Boyd 1.835 m², an average of 1.824 m².
Using BSA correctly
- Use current height and weight.
- Mosteller is the usual default for adults.
- Doses are set by clinicians, not calculators.
- Children often use Haycock or Mosteller.
Compare with the BMI Calculator, check body fat with the Army Body Fat Calculator, and convert units with the Weight Converter.
How it works: Height and weight are first converted to centimeters and kilograms if you entered inches and pounds. Each formula is then applied as published. The Mosteller value is highlighted because it is the most widely used in hospitals and the easiest to check by hand.
Features
Five formulas
Mosteller, Du Bois, Haycock, Gehan-George and Boyd.
Metric or US units
Centimeters and kilograms, or inches and pounds.
Square meters and feet
BSA in m² and ft², plus BMI for reference.
When to use it
Medical students and nurses
Check BSA calculations quickly. Compare with the BMI Calculator.
Understanding a prescription
See where a dose per square meter comes from.
Research
Index measurements to body size.
Metabolism
Compare with the BMR Calculator.
Related Health and Fitness tasks
Frequently asked questions
What is body surface area?
An estimate of the total surface area of the body, in square meters. It is used for some drug doses and to compare body functions between people of different sizes.
What is the Mosteller formula?
BSA (m²) = √(height in cm × weight in kg ÷ 3600). For 170 cm and 70 kg, BSA = √(11,900 ÷ 3600) = 1.818 m².
What is the Du Bois formula?
BSA = 0.007184 × weight^0.425 × height^0.725, from 1916. It is still common, though it was based on very few people.
Which BSA formula is best?
Mosteller is the most widely used because it is simple and accurate for adults. Haycock is often preferred for children. The formulas usually agree within a few percent.
What is a normal body surface area?
About 1.9 m² for adult men and 1.6 m² for adult women on average. Newborns are about 0.25 m².
Why are drugs dosed by BSA?
BSA tracks metabolic rate and kidney function better than weight alone, so some drugs with narrow safety margins, especially chemotherapy, are dosed per square meter.
Can I use this to dose medication?
No. Doses must be decided by a doctor or pharmacist, who may adjust for kidney function, weight and other factors.
How does BSA differ from BMI?
BMI relates weight to height to screen weight categories; BSA estimates the skin's surface area. They answer different questions.
What is the BSA formula for children?
Mosteller and Haycock are both used for children. Haycock was developed using infants, children and adults.
Do I need to convert pounds and inches?
No. Choose inches and pounds and the calculator converts them before applying the formulas.
Why do formulas give slightly different answers?
Each was fitted to different groups of people with different methods, so results differ by a few percent, more at extremes of size.
What is BSA used for besides dosing?
Indexing cardiac output (cardiac index), kidney filtration rate and burn area estimates to body size.
Does BSA change with weight loss?
Yes. BSA depends on weight and height, so it falls as weight falls.
What is the Mosteller formula in pounds and inches?
BSA = √(height in inches × weight in pounds ÷ 3131).
Built and reviewed by Hamza Farooq, founder and lead developer
· Last updated
· How we check our tools
· Report a problem