Calculate your BSA using the Du Bois formula — understand how body surface area drives chemotherapy dosing, cardiac index, and eGFR indexing in clinical medicine.
| Group | ft² | m² |
|---|---|---|
| Newborn child | 2.69 | 0.25 |
| Two-year-old child | 5.38 | 0.5 |
| Ten-year-old child | 12.27 | 1.14 |
| Adult female | 17.22 | 1.6 |
| Adult male | 20.45 | 1.9 |
This body surface area calculator accepts your height and weight in either US units (feet, inches, pounds) or metric units (centimeters, kilograms) and returns your BSA in square meters (m²). It uses the Du Bois formula, published in 1916 and still cited in pharmacology, oncology, and nephrology references worldwide. The result is useful to clinicians as a starting point for dosing certain drugs — particularly chemotherapy agents and some cardiac medications — and for standardizing physiological measurements like glomerular filtration rate (indexed GFR is reported per 1.73 m², the average adult BSA). The calculator is an educational and reference tool; actual drug prescribing requires individualized clinical judgment by a licensed provider. It is not a substitute for a pharmacist's dosing calculation.
Enter your height and weight in your preferred units and tap calculate — the tool returns your BSA in m² using the Du Bois formula. The average adult BSA is approximately 1.7–1.9 m², with men averaging around 1.9 m² and women around 1.7 m² in clinical literature. If your result falls in that range, it confirms typical scaling for most adult drug-dosing references. A pediatric BSA will be considerably lower (a 10 kg, 70 cm toddler scores roughly 0.46 m²), which is precisely why children can't simply receive weight-scaled adult doses of many medications — their BSA changes the whole pharmacokinetic profile. You don't need to do anything with the number directly; your provider uses it as one variable in a multi-factor dosing equation.
The Du Bois and Du Bois formula (1916) is:
BSA (m²) = 0.007184 × height (cm)^0.725 × weight (kg)^0.425
A 5'9" (175 cm), 170 lb (77.1 kg) adult calculates as: 0.007184 × 175^0.725 × 77.1^0.425 ≈ 1.93 m². An alternative, the Mosteller formula (BSA = √[height (cm) × weight (kg) / 3600]), is simpler and common in quick clinical settings, yielding results within about 2% of Du Bois for most adults. Both formulas assume standard proportions and are less accurate at the extremes of size.
Below are the most popular formulas for estimating BSA. The most widely used is the Du Bois formula. Where BSA is in m², W is weight in kg, and H is height in cm.
BSA = 0.007184 × W0.425 × H0.725
Du Bois D, Du Bois EF (Jun 1916). Archives of Internal Medicine 17 (6): 863-71.
BSA = √(H × W / 3600) = 0.016667 × W0.5 × H0.5
Mosteller RD. N Engl J Med 1987; 317:1098.
BSA = 0.024265 × W0.5378 × H0.3964
Haycock GB, Schwartz GJ, Wisotsky DH. J Pediatr 1978, 93:62-66.
BSA = 0.0235 × W0.51456 × H0.42246
Gehan EA, George SL, Cancer Chemother Rep 1970, 54:225-235.
BSA = 0.03330 × W(0.6157 - 0.0188 × log₁₀(W)) × H0.3
Boyd, Edith (1935). The Growth of the Surface Area of the Human Body. University of Minnesota.
BSA = 0.008883 × W0.444 × H0.663
Fujimoto S, et al. Nippon Eiseigaku Zasshi 1968;5:443-50.
BSA = 0.007241 × W0.425 × H0.725
Fujimoto S, et al. Nippon Eiseigaku Zasshi 1968;5:443-50.
Women: BSA = 0.000975482 × W0.46 × H1.08
Men: BSA = 0.000579479 × W0.38 × H1.24
Schlich E, Schumm M, Schlich M. Ernahrungs Umschau 2010;57:178-183.
BSA-based dosing arose from the observation that metabolic rate, and therefore drug clearance, scales better with surface area than with weight alone. Chemotherapy agents like cisplatin, carboplatin, and doxorubicin are routinely prescribed in milligrams per square meter (mg/m²) because the dose needs to saturate the body's tissues proportionally — too low and the cancer isn't hit hard enough; too high and the toxicity overwhelms the patient. The National Cancer Institute references BSA in the dosing guidelines for dozens of chemotherapy regimens. It also appears in cardiology: cardiac index, used to assess heart function, is cardiac output normalized to 1.73 m² BSA so cardiologists can compare outputs between a 120-pound woman and a 250-pound man on the same scale. That single standardization number — 1.73 m² — is the historical average adult BSA used as a reference point across nephrology and cardiology.
While dosing for chemotherapy is often determined using BSA, there exist arguments against its use for medications with a narrow therapeutic index. BSA may not be accurate enough at extremes of height and weight, and BMI may be a better estimate in such cases. Despite these limitations, chemotherapy dosages determined by BSA remain more consistent than those determined by body weight alone.
If you've ever seen kidney function reported as "eGFR per 1.73 m²," you've encountered BSA indexing without knowing it. The value 1.73 m² was established as the reference average adult body surface area, originally derived from early 20th-century physiological studies. When nephrologists report eGFR indexed to 1.73 m², they're adjusting your raw filtration rate so it can be compared apples-to-apples regardless of your body size. A very large man has more nephrons and will filter more by sheer volume; dividing by his BSA and multiplying by 1.73 m² brings his result onto the same scale as a smaller woman's. Your BSA calculator result lets you understand whether you're close to that reference point or significantly above or below it — which has clinical relevance for how your indexed lab values should be interpreted.
These two metrics serve completely different purposes. BMI — weight divided by height squared — is a population-level screening tool for weight status and cardiovascular risk stratification. BSA is a physiological scaling factor that corrects for the fact that bigger bodies need different absolute doses of many drugs and have different absolute levels of organ output. BMI says nothing about how much drug your liver can clear; BSA at least correlates with the metabolic infrastructure doing that clearing. That said, BSA is not a metabolic measurement — it doesn't assess body fat percentage, disease risk, or fitness. Clinicians use BMI to flag obesity-related risk, and they use BSA to scale interventions. You can have a high BMI and a normal BSA, or vice versa. Neither metric is superior; they answer different questions entirely.
BSA grows rapidly in childhood, and that growth is non-linear. A newborn's BSA is roughly 0.19 m², a 5-year-old's is about 0.73 m², and a 10-year-old's is around 1.14 m² — climbing steeply toward the adult range. This rapid scaling is why many pediatric drug doses are expressed per m² BSA rather than per kilogram: weight-based dosing alone can underestimate or overestimate exposure because body composition changes so dramatically from infancy through adolescence. Pediatric oncology protocols in particular rely heavily on BSA because the therapeutic index for chemotherapy is narrow and children's physiology doesn't map cleanly onto adult models. Parents researching a child's chemotherapy regimen will encounter BSA in every dose table, and understanding that your child's m² figure is simply a size-scaling factor — not a measure of health or illness — can make those numbers less alarming.
The Du Bois formula was derived from measurements of only nine subjects, which has led researchers to propose over 20 alternative equations over the decades. Studies comparing formulas have found that Du Bois can slightly underestimate BSA in obese adults — by roughly 5–8% at very high body weights — while formulas like Haycock and Gehan-George perform somewhat better at the extremes. Despite these limitations, Du Bois remains the most widely cited formula in clinical reference tools because its long history makes it the default standard in pharmacological literature. The Mosteller formula is popular for bedside mental math. For most adults with typical proportions, the difference between formulas is clinically negligible — less than 0.1 m². If you're using your BSA for educational reference, Du Bois is perfectly adequate.
Height and weight are the only direct inputs, but how they interact matters. Because the height exponent (0.725) is larger than the weight exponent (0.425) in the Du Bois formula, a taller person will see their BSA climb faster with added height than a shorter person gains from the same weight increase. Obesity inflates BSA, though less dramatically than it inflates BMI, which is one reason some drug-dosing protocols cap BSA at a maximum (often 2.2 m²) to avoid toxic overdosing in very large patients. Body composition — the ratio of muscle to fat — doesn't change the formula result, since only total dimensions matter. Age and sex affect average BSA indirectly through typical height and weight differences between demographic groups, not through any correction factor in the formula itself.
Jordan is 5'6" (167.6 cm) and 140 lb (63.5 kg). The Du Bois formula gives: 0.007184 × 167.6^0.725 × 63.5^0.425 ≈ 1.73 m² — almost exactly the standard clinical reference value. If Jordan's patient were prescribed a chemotherapy drug at 75 mg/m², the dose would be 75 × 1.73 = 129.75 mg, rounded to a practical dose by the oncologist.
Mateo is 6'2" (187.9 cm) and 230 lb (104.3 kg): 0.007184 × 187.9^0.725 × 104.3^0.425 ≈ 2.24 m². For a drug protocol that caps BSA at 2.2 m², the pharmacist would dose Mateo at the cap rather than his actual calculated value, illustrating why that ceiling exists and why your raw calculator result isn't always the clinical number used.
Use your most accurate, current measurements — BSA is sensitive to both height and weight, so a stale weight entry can shift your result meaningfully.
If you're computing BSA for reference alongside a medical prescription, always have a licensed pharmacist verify the actual drug dose — your calculator number is a starting point, not a final dosing authority.
Understand that very high-BSA results (above 2.0–2.2 m²) may be capped in chemotherapy protocols; your physician or pharmacist will apply that cap if needed.
Compare your BSA to the 1.73 m² reference to understand how your indexed lab values (like eGFR) relate to your actual biology — a BSA well above 1.73 m² means your raw GFR may look impressive but index more modestly.
If a pediatric BSA is what you need, double-check the weight and height inputs carefully — small errors produce larger percentage deviations in the pediatric range.
Average adult BSA is approximately 1.7–1.9 m², with the historical clinical reference set at 1.73 m². Men typically average around 1.9 m² and women around 1.7 m², though individual values depend entirely on height and weight. The Du Bois formula is the standard calculation method.
Most chemotherapy agents are dosed in milligrams per square meter (mg/m²) of BSA, so oncologists multiply your calculated BSA by the prescribed mg/m² figure to get your total dose. This approach scales the drug's therapeutic and toxic effects to your body size more consistently than weight-based dosing alone.
BSA (m²) = 0.007184 × height (cm)^0.725 × weight (kg)^0.425. This formula, published in 1916, remains the most widely cited in clinical pharmacology despite being derived from a small original dataset.
Kidney function is reported indexed to 1.73 m² — the historical average adult BSA — so results are comparable across people of different sizes. Your own BSA helps you understand how close you are to that reference body.
Both estimate BSA, but the Mosteller formula — BSA = √[height (cm) × weight (kg) / 3600] — is simpler and slightly different in result. For most adults the two values differ by less than 2%, which is clinically negligible in most settings.
Children's BSA is much lower and grows non-linearly from birth through adolescence, ranging from about 0.19 m² for a newborn to around 1.14 m² for a 10-year-old. Pediatric drug protocols dose per m² precisely because children's pharmacokinetics scale with BSA more reliably than with weight alone.
The calculator gives you the BSA figure used as an input to dosing, but actual dose verification must be done by a licensed oncology pharmacist who also considers creatinine clearance, organ function, and protocol-specific caps. Use this tool for educational reference only.
📏 Body Surface Area (BSA) is the total surface area of the human body, used clinically as a more accurate measure of metabolic mass than body weight.
💊 BSA is commonly used for chemotherapy dosing and calculating cardiac index.
📊 The Du Bois formula is the most widely used and has been shown effective for estimating body fat in both obese and non-obese patients.
👶 BSA varies by age: newborns (~0.25 m²), children (~0.5-1.14 m²), adult females (~1.6 m²), adult males (~1.9 m²).
Brief disclaimer: This calculator provides educational BSA estimates using the Du Bois formula. Results are for reference and educational purposes only. Actual drug dosing — particularly for chemotherapy, cardiac medications, and pediatric protocols — requires individualized clinical judgment by a licensed provider. BSA formulas assume standard body proportions and may be less accurate at extremes of size. Never use this calculator to verify or adjust a prescribed medication dose. Consult your physician or pharmacist for any medication-related questions.