Calculate your Body Surface Area (BSA) using the Mosteller formula, commonly used in medicine for drug dosing and clinical assessments.
A Body Surface Area (BSA) Calculator estimates the total surface area of a person's skin based on their height and weight. While it may sound like a niche measurement, BSA is a critical tool in clinical medicine, since it is used to calculate accurate dosages for chemotherapy drugs, certain other medications, and to assess cardiac and kidney function indices that are normalized per unit of body surface area rather than simply per kilogram of body weight.
Several validated formulas exist, with the Mosteller formula being one of the simplest and most widely used: BSA (m²) = square root of [(height in cm × weight in kg) ÷ 3600]. Other formulas such as Du Bois and DuBois, or the Haycock formula, use slightly different constants and exponents but generally produce very similar results for adults within a typical size range.
Enter your height and weight in metric or imperial units. The calculator applies the chosen formula and returns your estimated body surface area in square meters, which can then be used, under medical guidance, in dosage calculations or clinical index assessments.
Example 1: An adult who is 170 cm tall and weighs 70 kg has a BSA of the square root of (170×70)/3600 = square root of 3.30 ≈ 1.82 square meters using the Mosteller formula.
Example 2: A child who is 120 cm tall and weighs 25 kg has a BSA of the square root of (120×25)/3600 = square root of 0.833 ≈ 0.91 square meters, illustrating how BSA scales down significantly for smaller body sizes, which is exactly why pediatric drug dosing relies on it.
Certain physiological processes, including metabolic rate, cardiac output, and kidney filtration, correlate more closely with body surface area than with body weight alone, so BSA-based dosing, especially for chemotherapy, can achieve more consistent and safer drug exposure across patients of different sizes.
No single formula is universally considered "most accurate" for every population; Mosteller is popular for its calculation simplicity and reasonable accuracy across a wide size range, while Du Bois has a long clinical history, and different institutions may prefer different formulas based on their own validation studies.
No, BSA-based dosing must always be calculated and verified by a qualified healthcare professional, since medication safety depends on many additional factors beyond BSA alone, including kidney and liver function, other medications, and the specific drug's dosing guidelines.
Children have a higher surface-area-to-volume ratio than adults because of their smaller overall size, which is one reason pediatric drug dosing and fluid management calculations rely so heavily on BSA rather than weight alone.
Yes, BSA is also used to index certain cardiac measurements, such as cardiac output and stroke volume, and kidney function measures like glomerular filtration rate, allowing doctors to compare these values fairly across patients of very different body sizes.
Most standard BSA formulas were developed using data from average-sized adults, so they can become less accurate at the extremes of body weight, which is why some specialized formulas exist specifically for very high or very low body weight populations.
Most common BSA formulas, including Mosteller, do not include a separate gender term, relying only on height and weight, though some newer specialized formulas do incorporate gender-specific adjustments for improved precision in certain clinical contexts.
Square meters provide a convenient, clinically standardized unit that keeps typical adult BSA values in an easy-to-read range (roughly 1.5 to 2.2 for most adults), which has become the international medical standard for reporting and comparing this measurement.
Doctors also use body surface area percentages to estimate the extent of burn injuries, using reference charts like the Rule of Nines, which helps guide fluid resuscitation calculations and severity classification in emergency burn treatment.
BSA formulas provide a mathematical estimate rather than a direct physical measurement, and while they correlate closely with actual skin surface area for most body types, direct measurement techniques exist for research purposes when higher precision is required.
Since chemotherapy can cause significant weight changes during treatment, doctors periodically recheck weight and recalculate BSA to keep dosing accurate and safe throughout the course of therapy, rather than relying on a single measurement taken at the start.