Body Surface Area Calculator (BSA)
Use the Mosteller formula to calculate body surface area from height and weight for pediatric dosing and physiologic normalization.
Clinical disclaimer
Formula comparison
| Formula | Expression | Best fit | Why it matters |
|---|---|---|---|
| Mosteller | sqrt((height cm × weight kg) / 3600) | Fast bedside use and the default formula on this page. | Simple, widely used, and usually the first-choice formula for day-to-day pediatric calculation. |
| Haycock | 0.024265 × height(cm)^0.3964 × weight(kg)^0.5378 | Specialty settings or research where pediatric-specific validation matters. | Often discussed when a pediatric-focused alternative to Mosteller is needed. |
| Du Bois | 0.007184 × height(cm)^0.725 × weight(kg)^0.425 | Historical comparison and protocols that still reference legacy calculations. | Less convenient at the bedside and not usually the first formula families or clinicians are calculating manually. |
Worked pediatric examples
| Example | Height | Weight | Mosteller BSA | Note |
|---|---|---|---|---|
| Newborn example | 50 cm | 3.5 kg | 0.22 m² | Example only, not a normal-range table. |
| Toddler example | 86 cm | 12 kg | 0.54 m² | Example only, not a normal-range table. |
| School-age example | 125 cm | 25 kg | 0.93 m² | Example only, not a normal-range table. |
| Adolescent example | 160 cm | 50 kg | 1.49 m² | Example only, not a normal-range table. |
When to use
- Medication dosing protocols that reference body surface area (for example, oncology or specialty regimens).
- Normalizing physiologic measures (for example, GFR or cardiac output per square meter).
- Documenting BSA for clinical notes or order sets that require surface area.
How the formula works
The Mosteller formula estimates BSA using height and weight. It is widely used in pediatrics for medication dosing and normalizing physiologic measures to a standard body surface area.
- BSA = sqrt((height cm × weight kg) / 3600).
- Use accurate length/height measurements, especially in infants.
- Convert units consistently; this calculator handles conversions.
Related calculators
References
Frequently asked questions
This tool uses the Mosteller formula: BSA = sqrt((height cm × weight kg) / 3600). It is commonly used for pediatric dosing and physiologic normalization.
A BSA calculator is used to estimate body surface area for medication dosing that depends on surface area and for normalizing physiologic measurements.
Enter weight in kg or lb and height/length in cm or inches. The calculator converts to metric internally.
Yes, BSA can be calculated for infants and children. Ensure accurate length and weight measurements for reliable results.
No. Always follow medication guidelines and institutional protocols for pediatric dosing and adjustments.
Mosteller is the simplest and most commonly used bedside formula, which is why this calculator uses it as the default. Haycock and Du Bois are also used in some research or specialty contexts, so it helps to know which formula your protocol expects.