Five formulas compared
Mosteller, Du Bois, Haycock, Gehan-George and Boyd, with the gap between them.
Health & wellness
Body surface area (BSA) calculator
Body surface area estimated with five clinical formulas, for adults and children, with the gap between the results.
Height and weight
The result appears as soon as height and weight are entered. It also works for children.
Height
Estimated body surface area
Mosteller
m²
Skin surface estimated from height and weight, used in medicine to adjust some doses and to normalise measurements such as cardiac output.
By formula
- MostellerReference1987, the most used, easy to work out
- -
- Du Bois1916, the historical formula
- -
- Haycock1978, also built from children
- -
- Gehan-George1970, based on more than 400 measurements
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- Boyd1935, accurate at extreme weights
- -
Method & sources
The Mosteller formula, recommended for its simplicity and accuracy, gives the main result. Du Bois, Haycock, Gehan-George and Boyd are shown for comparison; they usually differ by less than 5%.
Formula
Mosteller: BSA = √(height cm × weight kg ÷ 3600) · Du Bois: BSA = 0.007184 × height^0.725 × weight^0.425Limitations
- Body surface area is an estimate from height and weight, not a direct measurement of the skin.
- The formulas diverge more for very young children and extreme builds.
- A body surface area result must never be the only basis for a treatment decision.
Was this tool useful?
How does this tool work?
Body surface area is the skin surface estimated from height and weight. Medicine uses it to adjust some drug doses and to compare measurements between people of different sizes. This calculator estimates it with five clinical formulas, for adults and children.
Enter height and weight in feet and pounds, stones or centimetres and kilograms: body surface area appears straight away in square metres, with the Mosteller formula as the main result.
The Du Bois, Haycock, Gehan-George and Boyd formulas are worked out alongside; the gap between the lowest and the highest shows the margin of uncertainty, usually a few hundredths of a m².
How to use this tool
Choose your units
Imperial, stones or metric: the measurements are converted before the calculation.
Enter height and weight
Use recent, accurate measurements, especially for children.
Read the result
Keep Mosteller, the reference, and the gap between the formulas in mind.
Good to know
Adults and children
Small heights and low weights are accepted.
Every unit
Feet and pounds, stones or centimetres and kilograms: the result updates as you type.
Body surface area formulas
Each formula combines height (cm) and weight (kg); the result is in square metres.
Mosteller
√(height × weight ÷ 3600)
Du Bois
0.007184 × height^0.725 × weight^0.425
Haycock
0.024265 × height^0.3964 × weight^0.5378
Gehan-George
0.0235 × height^0.42246 × weight^0.51456
- height
- Height in centimetres
- weight
- Weight in kilograms
These formulas give an estimate; calculating a dose is always a matter for the care team.
Use cases
Check a body surface area
Find the value used in a care protocol or a prescription.
Compare the formulas
See how much Mosteller, Du Bois, Haycock, Gehan-George and Boyd differ for the same person.
Work it out for a child
The Haycock and Mosteller formulas remain valid for small heights.
Tips and best practices
- Weigh and measure on the same day when body surface area is used for a dose calculation.
- In children, a small weight error changes the result noticeably: use accurate scales.
- Always compare with the value given by the care team, which may use a specific formula.
Frequently asked questions
How do I calculate body surface area?
With the Mosteller formula: the square root of (height in cm × weight in kg ÷ 3600). For 5 ft 7 in (170 cm) and 154 lb (70 kg), that is √(11,900 ÷ 3600) ≈ 1.82 m².
What is the average body surface area of an adult?
It is about 1.9 m² for a man and 1.6 m² for a woman. It varies mostly with height and weight.
Which body surface area formula should I use?
Mosteller is the most used because it is simple and accurate for adults and children. Du Bois remains the historical reference; Haycock is often used in paediatrics.
What is body surface area used for in medicine?
It is used to calculate the doses of some drugs, in particular in chemotherapy, to index cardiac output or kidney function, and to estimate the extent of burns.
Can I calculate a child’s body surface area?
Yes. The calculator accepts heights from 1 ft (30 cm) and weights from about 2 lb (1 kg). Haycock and Gehan-George were built including children.
Why do the formulas give different results?
They were built from different groups and do not weigh height and mass the same way. For most adults, the gap stays under 5%.
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