Body Surface Area Calculator
Calculate body surface area in m² with Mosteller, Du Bois, Haycock and four more formulas side by side. Then turn it into a mg/m² dose, a cardiac index, or a de-indexed kidney function for drug dosing, all in one pharmacist-built tool.
Written and fact-checked by Manzoor Ahmad, Pharm-DLast reviewed September 29, 2026
Clinical extras (optional)
For health professionals and students. Results are a cross-check, never a replacement for your protocol and independent verification.
Enter height and weight to calculate body surface area. Everything runs in your browser and nothing is stored.
Body surface area (Mosteller)
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Formula consensus
Each dot is one published formula. The shaded band is where they fall.
BSA vs the 1.73 m² reference
Spread between formulas
Clinical cross-checks
Enter a dose, cardiac output or eGFR in the clinical extras to see them here.
What is body surface area?
Body surface area (BSA) is the estimated total area of the outside of your body, measured in square meters (m²). The most widely used formula, Mosteller, is simple: BSA = √(height in cm × weight in kg ÷ 3600). A person who is 175 cm tall and weighs 75 kg has a BSA of about 1.91 m².
Average adult BSA is roughly 1.9 m² for men and 1.6 m² for women, and about 0.25 m² for a newborn. Clinicians use BSA because it tracks metabolic rate, blood volume and organ size better than weight alone, which is why it sits behind chemotherapy doses, cardiac index and the 1.73 m² standard used for kidney function.
How to use the body surface area calculator
- Enter height and weight in imperial or metric units. Use a measured height and a same-day weight whenever BSA feeds a dose, because an estimated or weeks-old weight is the most common source of error.
- Add sex and age. Neither changes the formulas, but they set the typical BSA reference for comparison and flag pediatric use.
- Pick the headline formula your protocol uses. Mosteller is the default; Haycock is popular in pediatrics; Du Bois appears in older references and some cardiology settings.
- Check the consensus strip. If all seven formulas sit close together, your BSA is robust. A wide spread usually means a very large, very small or unusually shaped body.
- Use the clinical extras for a mg/m² dose, a cardiac index from cardiac output, or an absolute eGFR from an indexed value. Every clinical figure must still be verified independently.
Body surface area formulas
All formulas below use weight (W) in kilograms and height (H) in centimeters and give BSA in m².
Mosteller formula (1987)
The simplest and most widely usedBSA = √(H × W ÷ 3600)
Published as a one-paragraph letter, Mosteller simplified the older Gehan and George equation into something anyone could work out with a calculator. It is now the default in most oncology software and pharmacy references.
Du Bois formula (1916)
The originalBSA = 0.007184 × W0.425 × H0.725
Du Bois and Du Bois derived their formula from careful surface measurements of just nine people. It has held up remarkably well for average adults, but it tends to underestimate BSA in people with obesity and in small children.
Haycock formula (1978)
Validated in infants, children and adultsBSA = 0.024265 × W0.5378 × H0.3964
Gehan and George formula (1970)
Derived from 401 measurementsBSA = 0.0235 × W0.51456 × H0.42246
Boyd formula (1935)
Weight in gramsBSA = 0.0003207 × H0.3 × Wg(0.7285 − 0.0188 × log₁₀ Wg)
Fujimoto formula (1968)
Derived in a Japanese populationBSA = 0.008883 × W0.444 × H0.663
Shuter and Aslani formula (2000)
Du Bois revisitedBSA = 0.00949 × W0.441 × H0.655
Shuter and Aslani re-examined the Du Bois approach with a larger set of measurements and published revised exponents, aimed at correcting some of the original formula’s bias across body sizes.
| Formula | Year | Best known for | Watch out for |
|---|---|---|---|
| Mosteller | 1987 | Oncology and general default | Very little; simple and well validated |
| Du Bois | 1916 | Historical standard, cardiology | Underestimates in obesity and infants |
| Haycock | 1978 | Pediatrics, from newborns up | Slightly higher than Mosteller in large adults |
| Gehan and George | 1970 | Basis for Mosteller | Rarely used directly now |
| Boyd | 1935 | Wide weight range, including infants | Complex to calculate by hand |
| Fujimoto | 1968 | Japanese populations | Lower values in Western adults |
| Shuter and Aslani | 2000 | Modern refit of Du Bois | Less familiar in clinical software |
Swipe the table sideways on a phone.
Which body surface area formula is most accurate?
For most adults of average build, the formulas agree within about 0.05 m², a difference that rarely matters. They drift apart at the extremes. In people with severe obesity, Du Bois and Fujimoto usually give the lowest values and Haycock or Boyd the highest. In small children, Du Bois performs poorly, which is why pediatric teams often prefer Haycock or Mosteller.
In practice, the most accurate formula is the one your protocol was designed around. Chemotherapy regimens, clinical trials and hospital policies usually specify one, most often Mosteller, and consistency across the whole treatment course matters more than small theoretical gains.
Body surface area chart (Mosteller, m²)
Find your weight in the rows and your height in the columns for a quick BSA estimate.
| Weight | 150 cm (4’11”) | 160 cm (5’3″) | 170 cm (5’7″) | 180 cm (5’11”) | 190 cm (6’3″) |
|---|---|---|---|---|---|
| 50 kg (110 lb) | 1.44 | 1.49 | 1.54 | 1.58 | 1.62 |
| 60 kg (132 lb) | 1.58 | 1.63 | 1.68 | 1.73 | 1.78 |
| 70 kg (154 lb) | 1.71 | 1.76 | 1.82 | 1.87 | 1.92 |
| 80 kg (176 lb) | 1.83 | 1.89 | 1.94 | 2.00 | 2.05 |
| 90 kg (198 lb) | 1.94 | 2.00 | 2.06 | 2.12 | 2.18 |
| 100 kg (220 lb) | 2.04 | 2.11 | 2.17 | 2.24 | 2.30 |
| 110 kg (243 lb) | 2.14 | 2.21 | 2.28 | 2.35 | 2.41 |
| 120 kg (265 lb) | 2.24 | 2.31 | 2.38 | 2.45 | 2.52 |
Average body surface area by age
| Age group | Typical BSA |
|---|---|
| Newborn | About 0.25 m² |
| 2 years | About 0.5 m² |
| 9 years | About 1.07 m² |
| 10 years | About 1.14 m² |
| 12 to 13 years | About 1.33 m² |
| Adult women | About 1.6 m² |
| Adult men | About 1.9 m² |
Averages vary between populations and over time as adult height and weight change.
BSA and chemotherapy dosing: a pharmacist’s view
Most of the BSA calculations I verify are for cancer medicines, where doses are written in mg/m². The calculation itself is easy; the judgment around it is where errors happen. These are the checks that matter most.
Use actual body weight, even in obesity
For years, many centers capped BSA at 2.0 m² or dosed on ideal weight for larger patients, fearing toxicity. The American Society of Clinical Oncology guideline on dosing in obese adults, first published in 2012 and reaffirmed in 2021, recommends full weight-based doses using actual body weight for most regimens, especially when treatment aims at cure. Underdosing can quietly reduce the chance of success. Caps are still written into some specific protocols, which is why the cap field here is optional and off by default.
Not every cancer dose uses BSA
Carboplatin is the classic exception: it is dosed to a target exposure (AUC) with the Calvert formula, which uses kidney function rather than BSA. Many newer targeted drugs and immunotherapies use flat doses or mg/kg. Always check the dosing basis before reaching for BSA.
Recalculate when weight changes
Many protocols ask for a new BSA when weight changes by more than about 5 to 10 percent. Weight loss during treatment is common, so a BSA from the first cycle can be wrong by the fourth.
Rounding and dose banding
Doses are often rounded to practical vial sizes or standard bands within a small percentage of the calculated dose. That is normal practice when the policy allows it, but the unrounded calculation should always be documented and double-checked by a second clinician.
BSA and kidney function: what 1.73 m² means
Lab reports give eGFR in mL/min per 1.73 m² because the value is scaled to an average adult body surface area. That is ideal for staging chronic kidney disease, but for drug dosing in people who are much larger or smaller than average, clinicians often convert it back to an absolute value:
De-indexed eGFRAbsolute eGFR (mL/min) = eGFR × BSA ÷ 1.73
A patient with a BSA of 1.4 m² and a reported eGFR of 60 actually clears about 49 mL/min, enough to change some doses. Enter an eGFR in the clinical extras to see this automatically. For medicines labeled with Cockcroft-Gault cut-offs, use the creatinine clearance calculator instead.
Cardiac index and other uses of BSA
Cardiac indexCardiac output divided by BSA. A normal resting cardiac index is roughly 2.5 to 4.0 L/min/m², so a cardiac output of 5 L/min means different things for a 1.5 m² and a 2.3 m² adult.
EchocardiographyHeart chamber sizes and valve areas are often indexed to BSA so results can be compared between people of different sizes.
Pediatric dosingSome pediatric medicines and fluids are calculated per m², where BSA matches physiology better than weight in very small children.
BurnsBurn size is described as a percentage of total body surface area using the rule of nines or Lund-Browder chart. That is a different estimate from the BSA calculated here.
Limitations of body surface area
- It is an estimate. Every formula was fitted to a limited group of people and gives an approximation of true skin area.
- Body composition is invisible to BSA. Two people with the same BSA can have very different amounts of fat and muscle. The lean body mass calculator helps when that matters.
- Amputation, fluid overload and edema distort weight-based estimates and need clinical judgment.
- For weight targets, BSA is not the right tool; use the ideal weight calculator or BMI calculator.
Body surface area calculator FAQ
The most common method is the Mosteller formula: BSA (m²) = √(height in cm × weight in kg ÷ 3600). For example, a person 170 cm tall weighing 70 kg has a BSA of √(11,900 ÷ 3600) = 1.82 m².
Average adult body surface area is about 1.9 m² for men and 1.6 m² for women. A newborn's BSA is about 0.25 m², rising to around 1.07 m² at age 9 and 1.33 m² at 12 to 13 years.
For average adults the major formulas agree within about 0.05 m². Mosteller is the most widely used and is the default in most oncology and pharmacy software. Haycock is preferred by many pediatric teams, and Du Bois can underestimate BSA in obesity and in infants. The best choice is the formula your protocol specifies, used consistently.
Body surface area correlates with metabolic rate, blood volume and organ size, so doses written in mg/m² aim to give people of different sizes similar drug exposure. The total dose equals the mg/m² dose multiplied by BSA.
ASCO guidance on obese adults recommends full weight-based dosing using actual body weight rather than routinely capping BSA, particularly when treatment aims at cure. Some specific regimens still include a cap, so always follow the protocol.
Mosteller (1987) is a simple square-root formula based on height and weight. Du Bois (1916) uses exponents derived from surface measurements of nine people. Results are close for average adults, but Du Bois gives lower values at higher body weights.
Use Mosteller or Haycock with the child's measured height in cm and weight in kg. Haycock was validated from newborns to adults. Pediatric doses based on BSA should always be checked by a pediatric pharmacist or physician.
BSA is used to calculate cardiac index (cardiac output divided by BSA), to index heart measurements on echocardiograms, to scale kidney function to 1.73 m², and for some pediatric medicines and fluid calculations.
Lab eGFR is scaled to a standard body surface area of 1.73 m² so results can be compared between people. To estimate actual kidney clearance for drug dosing in a person much larger or smaller than average, multiply eGFR by BSA and divide by 1.73.
Cardiac index is cardiac output in L/min divided by BSA in m². A typical resting cardiac index is about 2.5 to 4.0 L/min/m².
No. The rule of nines estimates what percentage of the body surface is burned. Body surface area formulas estimate the total size of that surface in square meters.
BSA changes more slowly than weight. With Mosteller, a 10 percent weight change alters BSA by about 5 percent. Many protocols recalculate BSA when weight changes by more than 5 to 10 percent.
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About the author
Manzoor Ahmad, Pharm-D
Pharmacist, health content writer and founder of DexoCalc
Manzoor is a Doctor of Pharmacy with more than nine years of experience writing about supplements, weight management and medication safety. He runs a community pharmacy where dose checks based on weight, body surface area and kidney function are part of everyday practice. He built this calculator from the original published equations and checks every formula against worked examples before release.
Sources and references
- Mosteller RD. Simplified calculation of body-surface area. New England Journal of Medicine. 1987;317(17):1098.
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Archives of Internal Medicine. 1916;17:863-871.
- Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults. Journal of Pediatrics. 1978;93(1):62-66.
- Gehan EA, George SL. Estimation of human body surface area from height and weight. Cancer Chemotherapy Reports. 1970;54(4):225-235.
- Boyd E. The Growth of the Surface Area of the Human Body. Minneapolis: University of Minnesota Press; 1935.
- Fujimoto S, Watanabe T, Sakamoto A, et al. Studies on the physical surface area of Japanese. Nippon Eiseigaku Zasshi. 1968;23(5):443-450.
- Shuter B, Aslani A. Body surface area: Du Bois and Du Bois revisited. European Journal of Applied Physiology. 2000;82(3):250-254.
- Griggs JJ, Mangu PB, Anderson H, et al. Appropriate chemotherapy dosing for obese adult patients with cancer: ASCO clinical practice guideline. Journal of Clinical Oncology. 2012;30(13):1553-1561; updated 2021.
- Calvert AH, Newell DR, Gumbrell LA, et al. Carboplatin dosage: prospective evaluation of a simple formula based on renal function. Journal of Clinical Oncology. 1989;7(11):1748-1756.
- KDIGO. Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International Supplements. 2013;3(1).
This body surface area calculator is for education and as a cross-check. BSA formulas are estimates. It is not a diagnosis and not a substitute for advice from your doctor, pharmacist or dietitian. Clinical doses, including chemotherapy, must follow the approved protocol and be independently verified by qualified professionals before use.