Comparing four body surface area equations
Estimate body surface area in square meters with the Mosteller, DuBois, Haycock, and Gehan–George formulas.
This page provides an equation-based estimate for education and planning. It does not diagnose a condition, measure an individual response, or replace professional care.
How to use this health calculator
- Choose appropriate inputs: Enter measurements using the units and ranges shown.
- Review the assumptions: Confirm that the model applies before interpreting the result.
- Calculate and interpret: Read the result together with its limitations and cautions.
- Use professional guidance when needed: Do not use a general calculator to change medication, treatment, or a clinician-directed plan.
Formula and variables
Each equation estimates external body surface area from height and weight. Imperial entries are converted to centimeters and kilograms before calculation.
Mosteller = √(height cm × weight kg ÷ 3600); DuBois = 0.007184 × H^0.725 × W^0.425; Haycock = 0.024265 × H^0.3964 × W^0.5378; Gehan–George = 0.0235 × H^0.42246 × W^0.51456- H — Height
- Height in centimeters after unit conversion.
- W — Weight
- Weight in kilograms after unit conversion.
Worked example: 180 cm and 80 kg
An adult enters a height of 180 cm and weight of 80 kg.
- Height
- 180 cm
- Weight
- 80 kg
- Mosteller: √(180 × 80 ÷ 3600).
- √4 = 2.00 m².
Result: The Mosteller estimate is 2.00 m²; the other formulas provide comparison estimates.
Formula results can differ because they were derived from different samples and mathematical models.
Understanding your results
Equation result
The numerical output follows the displayed formula and entered assumptions.
Personal interpretation
Individual biology, measurement error, environment, health conditions and medicines can change real-world outcomes.
Assumptions
- Height and weight are current and measured accurately.
- The selected metric or imperial unit system matches the entered numbers.
- A height-and-weight equation is appropriate for the intended educational comparison.
Limitations
- BSA is estimated rather than directly measured.
- Equation performance can differ in infants, children, obesity, edema, amputations, and unusual body proportions.
- Small numerical differences between equations may matter in some clinical contexts.
- The calculator does not select a formula for medication dosing or treatment.
Common mistakes
- Entering inches as centimeters or pounds as kilograms.
- Averaging formulas when a protocol specifies one equation.
- Rounding height or weight before calculation.
- Using a general web result to determine a medication dose.
Practical use cases
Educational estimate
Explore how the inputs affect the equation result.
Consistent tracking
Compare estimates only when methods, units and conditions are consistent.
Planning and decision guide
Treat cautions as part of the result
Clinical protocols may mandate a particular BSA equation, rounding method, dose cap, or independent verification.
Never initiate or change medication dosing from this calculator; use the prescribing protocol and qualified clinical review.
Escalate symptoms or clinical questions
Seek qualified medical advice for symptoms, diagnosed conditions, medicines, pregnancy, or individualized treatment decisions.
Frequently asked questions
Which BSA formula should I use?
Use the equation required by the relevant clinical or research protocol. Mosteller is simple, but no formula is universally correct.
Why do the results differ?
The equations use different coefficients and were derived from different samples.
Can I use BSA to calculate chemotherapy?
Not independently. Oncology dosing requires the prescribed regimen, protocol-specific rules, laboratory data, and professional verification.
Sources and review
- Simplified Calculation of Body-Surface Area — New England Journal of Medicine (PubMed record). Accessed 2026-08-03.
- Geometric Method for Measuring Body Surface Area: A Height-Weight Formula Validated in Infants, Children, and Adults — Journal of Pediatrics (PubMed record). Accessed 2026-08-03.
- Body Surface Area in Normal-Weight, Overweight, and Obese Adults: A Comparison Study — European Journal of Applied Physiology (PubMed record). Accessed 2026-08-03.
Reviewed 2026-08-03.