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Body Surface Area Formula Calculator
Sign up to favourite this calculatorCompare body surface area (BSA) estimates using five established height-and-weight formulas. Results are formula references for educational purposes and are not suitable for medication dosing, treatment decisions or clinical care.
BSA formula estimates
| Formula | Estimated BSA |
|---|---|
| Mosteller (1987) | 1.82 m² |
| Du Bois & Du Bois (1916) | 1.81 m² |
| Haycock (1978) | 1.83 m² |
| Gehan & George (1970) | 1.83 m² |
| Fujimoto (1968) | 1.76 m² |
For general information only. These formula estimates are not a medical assessment and do not replace advice from a qualified healthcare professional.
Do not use this calculator for medication dosing or treatment decisions.
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Assumptions and limits
- An estimate from the numbers you entered, for guidance only. It is not financial, tax or medical advice.
- Calculator version 1, last updated 25 October 2026.
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How to use this body surface area calculator
- Enter a height, and pick its unit — centimetres, metres, feet, inches, or feet and inches.
- Enter a weight, and pick its unit — kilograms, pounds, or stones and pounds.
- Read the estimate from each of the five formulas in the comparison table.
Nothing is submitted anywhere. The calculation runs in the page as you type, and the link in your address bar carries the figures, so it can be shared or bookmarked.
What do I need to enter?
- Height — in centimetres, metres, feet, inches, or feet and inches. Accepted from 130 cm to 220 cm, whichever unit you use.
- Weight — in kilograms, pounds, or stones and pounds. Accepted from 30 kg to 300 kg, whichever unit you use.
What do the results show?
- BSA formula estimates — one row per formula: Mosteller (1987), Du Bois & Du Bois (1916), Haycock (1978), Gehan & George (1970) and Fujimoto (1968).
- Each estimate is in square metres (m²) to two decimal places. The formulas give slightly different values, and no average or recommended figure is shown.
How is body surface area calculated?
Each formula is calculated independently from height and weight. Every one takes height in centimetres and weight in kilograms, so any unit you enter is converted first. Because the equations use different coefficients and different height and weight exponents, their results may differ for the same measurements.
This page intentionally displays the individual formula estimates rather than one averaged or recommended body surface area. A clinical setting may require a particular validated formula and professional judgement, which is a decision for a prescriber or protocol, not for this calculator.
Body surface area does not classify a weight category the way the BMI Calculator does. For a similar comparison of several published formulas from the same height and weight, see the Ideal Body Weight Calculator.
Mosteller BSA [m²] = √(Height [cm] × Weight [kg] ÷ 3600)
- Du Bois & Du Bois = 0.007184 × Height [cm]0.725 × Weight [kg]0.425
- Haycock = 0.024265 × Height [cm]0.3964 × Weight [kg]0.5378
- Gehan & George = 0.0235 × Height [cm]0.42246 × Weight [kg]0.51456
- Fujimoto = 0.008883 × Height [cm]0.663 × Weight [kg]0.444
Worked example. At 170 cm and 70 kg, the Mosteller formula gives √(170 × 70 ÷ 3600) = 1.82 m². For the same measurements Du Bois & Du Bois gives 1.81 m², Haycock 1.83 m², Gehan & George 1.83 m² and Fujimoto 1.76 m² — for an average adult build the five formulas typically sit within about a tenth of a square metre of one another.
Limitations of body surface area formulas
- Every formula is an estimate fitted to a limited historical sample, not a direct measurement of a person's body.
- Results can diverge more for people well outside an average adult height and weight range.
- This is a formula reference for general adult use, not a medical assessment. Do not use it for medication dosing, chemotherapy dosing, fluid or burn treatment, or other clinical decisions.
- It is not designed for paediatric or clinical use, and it does not replace advice from a qualified healthcare professional.
Frequently asked questions
Why do BSA formulas give different answers?
Each body surface area formula was fitted to a different, relatively small sample of directly measured people, so each one uses its own constant and its own height and weight exponents. Mosteller takes a square root of height times weight over 3600; Du Bois & Du Bois raises height to the power 0.725 and weight to 0.425. Fed the same height and weight, the five formulas here normally sit within about a tenth of a square metre of one another for an average adult build, and diverge more towards the extremes of height and weight.
Which BSA formula is best?
This calculator does not select a best formula, and none is universally "correct". Du Bois & Du Bois (1916) is the oldest and most cited; Mosteller (1987) is the simplest to compute. A clinical setting that uses BSA will specify the particular validated formula it requires — that choice is made by the prescriber or protocol, not by this page.
Can I use this calculator for medication or chemotherapy doses?
No. These results are a formula reference for education only. Do not use them to calculate medication doses, chemotherapy doses, fluid treatment, burn treatment or any other clinical decision. Dose calculations must use the formula your prescriber or pharmacy specifies and be confirmed by a qualified professional.
Is this calculator for children?
No. This formula comparison is intended for general adult reference only. It is not designed for paediatric or clinical use. For a child or young person, speak with a GP or another qualified health professional.
Does body surface area depend on sex?
No. Every published BSA formula shown here uses only height and weight, with no separate constants for men and women.
What units does this BSA calculator use?
Every formula is calculated in square metres (m²). You can enter height in centimetres, metres, feet, inches, or feet and inches, and weight in kilograms, pounds, or stones and pounds — each value is converted to centimetres and kilograms before the formulas run.
Last updated 25 October 2026.