How to use Body Surface Area Calculator
Body surface area (BSA) is the total surface area of the human body, expressed in square metres, and it is used in medicine to scale certain measurements and drug doses to a person’s size more accurately than weight alone. Because BSA cannot be measured directly, it is estimated from height and weight using validated formulas. This calculator computes BSA with the Mosteller formula — the most widely used — and also shows the Du Bois and Haycock results so you can compare. Enter your measurements in metric or imperial units and the conversion is handled for you.
- Choose metric (cm, kg) or imperial (in, lb).
- Enter your height.
- Enter your weight.
- Read your BSA from the Mosteller formula.
- Compare the Du Bois and Haycock estimates in the table.
Your data never leaves your device — 100% private processing.
The formulas behind BSA
Several equations estimate body surface area, each derived from measurements of real people, and they agree closely for typical adults. The Mosteller formula is the simplest: BSA equals the square root of height in centimetres times weight in kilograms divided by 3600. Its simplicity and accuracy have made it the default in many clinical settings. The older Du Bois and Du Bois formula uses height and weight raised to fractional powers and is still referenced widely. The Haycock formula was developed with data that included children, so it is often chosen in paediatrics. This tool reports all three. For an average-sized adult they typically fall within a few percent of one another; differences become more noticeable at the extremes of height and weight, which is one reason a clinician may prefer a particular formula for a particular patient.
| Formula | Basis |
|---|---|
| Mosteller | √(height × weight / 3600) |
| Du Bois | 0.007184 × height^0.725 × weight^0.425 |
| Haycock | 0.024265 × height^0.3964 × weight^0.5378 |
Why BSA is used in medicine
Many physiological quantities — cardiac output, glomerular filtration rate, and the dosing of some chemotherapy and other drugs — correlate better with surface area than with body weight, because surface area tracks metabolic rate more closely. Scaling a dose to BSA aims to give patients of different sizes a comparable exposure to a medicine. That said, BSA-based dosing is an active area of clinical judgement: it can over- or under-estimate for people at the extremes of size, and some protocols cap or adjust the calculated value. For that reason this calculator is strictly a general-information and educational tool. It should never be used to determine or change a real medication dose; that is a decision for a qualified prescriber working from the full clinical picture and the specific drug’s guidance.
Worked examples
Average adult
Inputs: 175 cm · 70 kg
Result: BSA ≈ 1.84 m² (Mosteller)
Imperial input
Inputs: 69 in · 154 lb
Result: BSA ≈ 1.84 m² (Mosteller)
Glossary
- BSA
- Body surface area — the total area of the body in square metres.
- Mosteller formula
- A simple, widely used equation for estimating BSA from height and weight.
- Du Bois formula
- A classic BSA equation using fractional powers of height and weight.
- Haycock formula
- A BSA equation derived with paediatric data, often used for children.
- Dosing
- Determining the amount of a medicine, sometimes scaled to BSA.
Related reading
Frequently Asked Questions
Why use Body Surface Area Calculator?
- Estimates BSA in m² from height and weight
- Shows Mosteller, Du Bois and Haycock results together
- Accepts metric or imperial units
- Highlights the widely used Mosteller value
- Runs in your browser — no data is uploaded
Common use cases
- Understand a BSA figure mentioned by a clinician
- Compare the main BSA formulas for the same person
- Estimate BSA for educational or reference purposes
- Convert height and weight into a size-scaled metric
- Check how unit choice affects the calculation
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