Body Surface Area Calculator

A body surface area (BSA) calculator estimates your body's total outer surface in square meters from just your height and weight. For a 5′9″ (175 cm), 160 lb (72.6 kg) adult, the Mosteller formula gives a BSA of about 1.88 m². This tool computes the Du Bois, Mosteller, Haycock and Gehan-George formulas side by side, then averages them so you get one robust figure.

Clinicians use BSA to scale measurements and some drug doses to body size: many chemotherapy drugs are dosed in mg per m², the cardiac index divides cardiac output by BSA, and kidney function (eGFR) is reported per 1.73 m² of BSA.

BSA answers a size-scaling question, so it is a different tool from our other body metrics. Use the BMI Calculator to check weight relative to height, the BMR Calculator for resting calories burned, the TDEE Calculator for total daily energy including activity, and the Calorie Calculator to plan intake. BSA on its own tells you none of those.

The BSA formulas

The historic and most-cited method is the Du Bois & Du Bois formula:

A simpler and extremely popular alternative is the Mosteller formula, which is easy to compute by hand:

This tool also reports the Haycock (often used for children) and Gehan-George formulas, then averages all four so you can see a consensus value. Every formula uses metric units internally, so your imperial pounds and feet/inches are converted first.

What is a normal BSA?

There is no healthy range for BSA. As a reference point, the CDC's latest body-measurement data (NHANES, August 2021 to August 2023) put the average US man at 175.1 cm and 199 lb and the average woman at 161.2 cm and 171.8 lb, which work out to a Mosteller BSA of about 2.10 m² and 1.87 m². The often-quoted 1.73 m² is a normalization constant, not today's average: kidney function (eGFR) is reported per 1.73 m². Children have a much smaller BSA in absolute terms but more surface area per pound of body weight (a 3.5 kg newborn has about 2.4 times the m² per kg of a 160 lb adult), which is one reason pediatric dosing needs care.

Body surface area chart by height and weight

Wondering what your BSA is for a given height and weight? The table below lists the Mosteller BSA in m² for common US height and weight combinations. Find your row and column to read your estimate.

Values use the Mosteller formula, BSA = √(kg × cm ÷ 3600), with 1 lb = 0.4536 kg and 1 in = 2.54 cm. For typical adults, Du Bois, Haycock and Gehan-George land within about 2% of these figures.

Where BSA is actually used

• Chemotherapy dosing: many cancer drugs are prescribed in mg per m² of BSA.
• Cardiac index: cardiac output divided by BSA, to compare hearts across body sizes.
• Burn care: burn size is described as a percentage of total body surface area, although that percentage is estimated with body charts rather than these formulas.
• Kidney function: GFR is normalized to a standard 1.73 m² BSA.

Because dosing protocols can include drug-specific maximum doses, dose banding, or adjustments for kidney and liver function, the number from any online calculator is a starting estimate only.

How to use this BSA calculator

You only need two measurements: height and weight. Work through the calculator in order:

1. Pick your units: leave it on imperial to enter feet/inches and pounds (the US default), or switch to metric for centimeters and kilograms. Values you already typed are converted, and everything is computed in kg and cm internally.
2. Enter your height: type your height in the selected unit. For imperial, use the feet and inches fields together (for example 5 ft 9 in).
3. Enter your weight: use a recent, accurate figure. Even a few pounds changes the BSA slightly, so use scale weight rather than a rough guess.
4. Read the results: the calculator shows the Du Bois, Mosteller, Haycock, and Gehan-George values in m² plus their average. For typical adults they land within a couple of percent of each other.

There is nothing to submit; the values update instantly as you type. If a number looks far too large or small, double-check that the right unit toggle is selected.

Who this calculator is for

BSA matters to more people than just oncologists. This tool is useful for:

• Patients and caregivers who have heard a dose described "per square meter" and want to understand the number behind it.
• Nursing and pharmacy students checking their hand calculations against multiple formulas.
• Clinicians who want a quick cross-check of Du Bois against Mosteller, Haycock, and Gehan-George.
• Researchers normalizing physiological measurements, like cardiac output or GFR, to body size.
• Anyone curious about how surface area scales with height and weight compared with simpler measures like BMI.

Worked example: comparing all four formulas

Take a person who is 5′6″ (168 cm) and 140 lb (63.5 kg). Running the numbers gives:

• Du Bois: about 1.72 m²
• Mosteller: about 1.72 m²
• Haycock: about 1.72 m²
• Gehan-George: about 1.73 m²

The four results cluster within roughly 1%, landing essentially on the 1.73 m² reference value. For typical adults the formulas agree this closely, so a much larger gap usually points to a data-entry error (such as a unit mix-up) or an unusual body size rather than a real disagreement.

To see the arithmetic behind the number, here is the Mosteller and Du Bois calculation stepped out for a 5′9″, 160 lb adult (69 in = 175.26 cm; 160 lb = 72.57 kg):

The Haycock (1.884 m²) and Gehan-George (1.890 m²) formulas land within 0.6% of these, and the four-formula average is 1.88 m².

Key terms explained

• Body surface area (BSA): the total external surface of the body in m². It grows with both height and weight, so it captures overall body size better than weight alone.
• Cardiac index: cardiac output divided by BSA. Indexing to BSA lets doctors compare a small and a large person's heart performance fairly.
• GFR (glomerular filtration rate): a measure of kidney function conventionally reported per 1.73 m² of BSA, so results are comparable across body sizes.
• Du Bois exponents: the powers 0.425 (weight) and 0.725 (height) in the Du Bois formula, fitted to early surface-area measurements.
• Dose banding / capping: rounding BSA into bands or limiting it to standardize doses in some protocols.

BSA vs. BMI: what is the difference?

Both BSA and BMI combine height and weight into a single number, but they answer different questions. BMI (weight ÷ height²) is a screening proxy for whether someone is under- or over-weight relative to height, and it has fixed category cutoffs (for example, 18.5 to 24.9 is the healthy-weight range). BSA, by contrast, estimates physical surface area and has no healthy range: a larger BSA simply means a larger body, not a better or worse one. Clinicians reach for BMI to talk about weight status and risk, and for BSA to scale doses and physiological measurements to body size. If you are interested in weight relative to height, the BMI Calculator and Ideal Weight Calculator are the right tools; BSA answers a separate, dosing- and physiology-focused question.

The four formulas compared

This calculator runs four published formulas at once. They were each fitted to different study populations, which is why they exist side by side rather than one replacing the others:

• Du Bois & Du Bois (1916): the original and most-cited formula, derived from just nine subjects. It uses two separate exponents and remains the historic reference; a 2000 reanalysis found it adequate in adults but criticized the tiny sample.
• Mosteller (1987): a single square-root formula published as a short letter so that BSA could be computed quickly by hand or on a basic calculator. For the adult profiles below it agrees with Du Bois within about 1.5%.
• Haycock (1978): derived from geometric measurements of 81 people from premature infants to adults. The same study found that Du Bois increasingly underestimates surface area below 0.7 m², by about 8% in newborns, which is why Haycock is often used for children.
• Gehan & George (1970): fitted to a much larger set of direct surface-area measurements than Du Bois had, across a wide range of body sizes.

By showing all four plus their average, the tool turns "which formula should I use?" into a non-issue for most people: when the values cluster tightly, any of them is a safe estimate. A wide spread, on the other hand, is a red flag that your height or weight entry is off.

Du Bois vs Mosteller vs Haycock vs Gehan-George

How much do the formulas actually differ for the same person? The table runs all four across five body profiles and shows the spread: the gap between the highest and lowest result as a percent of the average. For these profiles it stays at or below about 2%.

All values in m², computed with each published formula after converting to kg and cm. Spread = (max − min) ÷ average.

How BSA scales with height and weight

BSA does not grow in a straight line with either measurement. Because the Du Bois exponents are 0.425 for weight and 0.725 for height, height has a noticeably larger effect on surface area than weight does, pound for pound. In practical terms, a tall, slim person and a shorter, heavier person can share almost the same BSA even though they look very different and have very different BMI values. This is the core reason BSA is useful: it captures overall body size in a way that a single weight reading cannot, while still being far simpler to obtain than a direct measurement.

The diminishing-returns shape also explains why BSA-based doses grow more slowly than weight-based ones. Doubling a person's weight does not double their surface area (with Du Bois it raises BSA by about 34%), so a dose scaled by BSA rises less steeply than one scaled by weight.

BSA, BMI and body composition together

BSA, BMI and body-composition tools each answer a different question, and they are most useful read together rather than in isolation:

• BSA tells you how large the body is overall, for scaling doses and physiological measurements.
• BMI tells you whether weight is high or low relative to height, as a quick health-risk screen; calculate it with the BMI Calculator.
• Body composition tells you how much of that weight is fat versus lean tissue, which the height-and-weight formulas cannot see. For that, use the Body Fat Calculator or the Lean Body Mass Calculator.

For example, two people with identical BSA might have very different body-fat percentages; BSA alone treats them the same. If your underlying goal is fitness or metabolic planning rather than dosing, a BMR Calculator or Calorie Calculator will be far more relevant than surface area.

A short history of body surface area

The idea of relating drug doses and metabolism to surface area rather than weight goes back to the 19th century, but it was the 1916 paper by Delafield Du Bois and Eugene Du Bois that gave clinicians a usable equation. Working with only nine subjects, they measured surface area directly and then fitted a formula to height and weight. That century-old equation is still widely used.

Later researchers refined the approach with larger samples and simpler math: Gehan and George (1970) with a much larger set of measurements, Haycock (1978) with 81 subjects from premature infants to adults, and Mosteller (1987) with a square-root shortcut that fits on the back of an envelope. For typical adults the four still agree within a few percent.

Tips for an accurate BSA estimate

• Use recent, measured numbers. A fresh scale weight and a properly measured height beat rounded guesses; even a few pounds or an inch shifts the result.
• Double-check the unit toggle. The single most common error is entering pounds or inches with the metric toggle on (or vice versa). If the result looks impossible, this is almost always why.
• Treat the average as your headline number. When the four formulas agree, their mean is a robust single figure to quote.
• For children, lean on Haycock. It was validated from premature infants up, but any actual pediatric decision belongs to a clinician.
• Don't over-interpret tiny differences. A 0.01 to 0.03 m² gap between formulas is normal, not a meaningful disagreement.

Limitations and assumptions

BSA formulas are convenient but not exact. Keep these limits in mind:

• They were derived from small validation samples (Du Bois used just nine people) and assume an average body shape.
• They use only height and weight, so they ignore body composition, fluid status, edema, and amputations.
• Accuracy drops at the extremes: very small infants and very high body weights fall outside the original validation range.
• Different formulas use different exponents, so a small spread between them is expected, not an error.
• The output is an estimate for standardizing measurements, never a substitute for a clinician's dosing decision.

How it compares to related calculators

This page answers "how large is my body surface area, in m²?" If your real question is different, a sister tool will fit better:

• To check whether your weight is healthy for your height, use the BMI Calculator.
• To find a target weight for your height and frame, use the Ideal Weight Calculator.
• To separate fat from lean mass, use the Body Fat Calculator or the Lean Body Mass Calculator.
• To plan energy needs, use the BMR Calculator for resting metabolism or the Calorie Calculator for daily intake.

Sources

• Du Bois D, Du Bois EF (1916, reprinted 1989): A formula to estimate the approximate surface area if height and weight be known.
• Mosteller RD (1987): Simplified calculation of body-surface area, New England Journal of Medicine.
• Haycock GB, Schwartz GJ, Wisotsky DH (1978): Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults, Journal of Pediatrics.
• Gehan EA, George SL (1970): Estimation of human body surface area from height and weight, Cancer Chemotherapy Reports.
• Shuter B, Aslani A (2000): Body surface area: Du Bois and Du Bois revisited (nine subjects).
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK): Glomerular filtration rate equations (eGFR reported per 1.73 m²).
• CDC National Center for Health Statistics (2025): Anthropometric Reference Data for Children and Adults, August 2021 to August 2023 (average adult height and weight).
• Griggs JJ, et al. (2012): Appropriate chemotherapy dosing for obese adult patients with cancer, ASCO clinical practice guideline.