MariposasBody Surface Area Calculator
By Zachary, builder of Mariposas · Reviewed against published exercise-science sources (references)
· Last updated June 2026
Body Metrics Body surface area (BSA) is sometimes used in clinical and physiology contexts. This computes it from your height and weight using the widely-used Mosteller formula.
⚕️ A general-information estimate from population-level formulas, a starting point, not a precise measurement and not medical advice.
How it works
The Mosteller formula calculates body surface area by taking the square root of (height in centimeters multiplied by weight in kilograms, divided by 3600). It produces a result in square meters, and for most adults that lands somewhere between 1.5 and 2.2 m². The reason clinicians reach for BSA rather than raw body weight is that many physiological processes, particularly cardiac output, kidney filtration rate, and drug metabolism, scale more predictably with surface area than with mass alone. A very muscular 200-pound person and a similarly scaled 200-pound person carrying more fat will have the same weight but meaningfully different surface areas, which matters when precision is the goal. Mosteller became the dominant formula in clinical practice largely because of its computational simplicity without sacrificing much accuracy compared to more complex alternatives like the DuBois or Haycock formulas.
When to use it
This calculator is most relevant to people researching how BSA-based drug dosing or physiological benchmarks are derived, athletes and coaches comparing cardiovascular output data that has been indexed to body surface area, and anyone curious about how their size translates into the metric used in a lot of exercise physiology literature. It also comes up in contexts like estimating sweat rate per unit area or understanding cardiac index values from a VO2 test report.
Worked example
Take a person who is 175 cm tall and weighs 80 kg. Plugging into the Mosteller formula: multiply 175 by 80 to get 14,000, divide by 3600 to get roughly 3.889, then take the square root to arrive at approximately 1.97 m². That result sits right in the middle of the typical adult range, which means if this person were reviewing a cardiology report that listed their cardiac output as 9.8 liters per minute, they could divide by 1.97 to get a cardiac index of about 4.97 L/min/m², a figure that can then be compared against population norms. Without the BSA calculation, that raw cardiac output number is harder to interpret across people of different sizes.
Tips for an accurate result
- Use your height and weight measured on the same day, ideally in the morning before eating, since hydration and food can shift your weight by a kilogram or more and that affects the output.
- Enter height in centimeters if you normally think in feet and inches. Five feet nine inches is 175.3 cm. A small conversion error of a few centimeters can nudge your BSA result noticeably.
- If you are using the BSA result to interpret a lab report or exercise test, check whether the original data used Mosteller or a different formula. DuBois values run slightly lower for larger individuals, so the formula choice can matter when comparing your number to reference ranges.
- BSA is a static snapshot based on your current measurements. If you are tracking changes in body composition over months, re-run the calculator periodically rather than assuming your initial result still applies.
- Keep in mind that BSA reflects external surface area estimated from height and weight. It does not account for body composition, so two people with the same height and weight but different muscle-to-fat ratios will get the same BSA result even though their physiology differs in other meaningful ways.
Formula & sources: methodology · references.
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- How is BSA different from BMI?
- BMI divides weight by height squared and produces a dimensionless number used mainly as a rough population-level screening tool. BSA actually estimates the physical surface area of your body in square meters, which scales differently. BSA grows more slowly than weight as a person gets heavier, which is part of why it tracks certain physiological variables better than raw weight does.
- Why do oncologists use BSA for chemotherapy dosing?
- Many chemotherapy agents have a narrow window between a therapeutic dose and a toxic one. Dosing by BSA rather than flat body weight accounts for the fact that larger people generally have higher blood volumes, faster drug clearance, and different distribution volumes. It is not a perfect system and there is ongoing research into alternatives, but BSA-based dosing has decades of clinical data behind it.
- What is a normal BSA for adults?
- Most published reference ranges place average adult BSA around 1.7 to 1.9 m² for women and 1.9 to 2.1 m² for men, though those are population averages and not targets. Taller or heavier individuals will sit above those figures, and smaller-framed adults will sit below them, without that implying anything about health status.
- Does BSA change if I lose or gain weight?
- Yes, because weight is one of the two inputs. A 10 kg change in body weight shifts BSA by roughly 0.05 to 0.1 m² depending on where you are starting from, since the relationship is not linear. The effect of height is proportionally larger per unit change, but height is stable in most adults, so weight fluctuations are the main driver of BSA changes over time.
- Can I use this calculator for children?
- The Mosteller formula does apply to pediatric populations and is used in pediatric oncology dosing, but reference ranges for what constitutes a typical BSA differ substantially by age. A 10-year-old and an adult will not share the same norms. If you are researching a child's BSA in a clinical context, any interpretation should be done with a healthcare provider who has pediatric reference data in hand.