Body Surface Area (BSA) Calculator
Compute BSA in m² with five classic formulas — DuBois, Mosteller, Haycock, Gehan & George, Boyd — side by side, plus their average and an optional mg/m² → dose conversion.
Your measurements
Enter height in centimeters or inches.
Enter weight in kilograms or pounds.
Results
Average BSA (5 formulas)
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| Formula | BSA (m²) |
|---|
Total dose at given mg/m² (average BSA)
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Educational estimate only — confirm every dose with a doctor or pharmacist.
The formulas
Constants verified against the original publications and standard medical references before this tool was released.
Worked examples
All values were recomputed from the published formulas and cross-checked by an independent calculation before release.
Frequently asked questions
What is the DuBois formula for body surface area?
The DuBois & DuBois (1916) formula is BSA (m²) = 0.007184 × weight(kg)^0.425 × height(cm)^0.725. For a 70 kg, 175 cm adult it gives about 1.85 m². It is the historical reference standard, though newer formulas are preferred for some populations.
What is the Mosteller BSA formula?
The Mosteller (1987) formula is BSA (m²) = √[height(cm) × weight(kg) / 3600]. It is the simplest of the common formulas and widely used clinically because it is easy to memorize and accurate enough for most dosing decisions.
What are the Haycock, Gehan & George, and Boyd formulas?
Haycock (1978): 0.024265 × W^0.5378 × H^0.3964, often preferred for children. Gehan & George (1970): 0.0235 × W^0.51456 × H^0.42246, used in some chemotherapy protocols. Boyd (1935): 0.0003207 × H^0.3 × Wg^(0.7285 − 0.0188·log10(Wg)) with weight in grams. All give BSA in m² with W in kg (grams for Boyd) and H in cm.
What is BSA used for in medicine?
Body surface area is used to dose drugs with narrow therapeutic windows (especially chemotherapy in mg/m²), to compute cardiac index (cardiac output ÷ BSA), and to normalize kidney function and metabolic measurements to body size. It correlates better with metabolic rate and blood volume than weight alone.
How do I convert a mg/m² dose to a total dose?
Multiply the dose rate by the BSA: total dose (mg) = mg/m² × BSA (m²). For example, a drug prescribed at 100 mg/m² for a patient with BSA 1.85 m² gives 185 mg. This calculator performs that multiplication automatically from the average BSA, but the result is educational only — always confirm dosing with a doctor or pharmacist.
Why do the five formulas give slightly different results?
Each formula was fitted to a different study population (different sizes, ages, and eras), so they extrapolate slightly differently. For typical adults the five formulas usually agree within about 2–3%. Averaging them, as this tool does, gives a balanced estimate for educational comparison.
Can BSA formulas be used for children and infants?
Formulas such as Haycock and Boyd were specifically validated on children and are generally preferred for pediatric estimates. However, pediatric dosing involves many factors beyond BSA, so any result here must be reviewed by a pediatrician or pharmacist before use.
Is this BSA calculator a substitute for medical advice?
No. This tool is for education only and is not a substitute for a doctor's or pharmacist's judgment. Never change a medication dose based on a web calculator — always verify dosing with a qualified clinician.
Free tool by NRTechStudio