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Body Surface Area Calculator

Health

Calculate your body surface area (BSA) in m² using three formulas — Mosteller, DuBois, and Boyd. Used in medicine for drug dosing and burn assessment.

Reviewed by the thecalcu.com team · Last updated July 25, 2026

Body Weight
kg
10200
Height
cm
100220

Average BSA for Indian adults: 1.60–1.70 m² (male) · 1.45–1.55 m² (female). Western reference: 1.73 m².

BSA — Mosteller (1987)

—m²

current clinical standard for oncology dosing

Formula Comparison

Mosteller1987Standard
— m²

Current clinical standard · most widely used in oncology

DuBois & DuBois1916
— m²

Original formula · older protocols may specify this

Boyd1935
— m²

Best accuracy at extreme weights · preferred in paediatric oncology

What is a BSA?

The Body Surface Area Calculator computes your total body surface area in square meters from just two numbers, weight and height, using three established clinical formulas: Mosteller, DuBois, and Boyd. BSA is a foundational measurement in medicine, most commonly used to dose chemotherapy drugs, but it also shows up in burn injury assessment and intensive care monitoring.

Unlike weight or BMI, BSA captures how body mass is distributed across a three-dimensional surface, which turns out to predict drug distribution and physiological effect more reliably than weight alone for many medications. This calculator runs all three formulas side by side, with Mosteller highlighted as the primary result since it's the current default across most oncology protocols and clinical software.

Who Should Use This Calculator?

Patients and caregivers navigating a chemotherapy protocol who want to understand how a dose was calculated, or how a recent weight change might shift the number at the next cycle.

Nurses, clinical pharmacists, and other healthcare staff who need a fast bedside or pharmacy-counter reference, especially when a protocol specifies a formula other than the one built into their primary charting software.

Medical and pharmacy students working through pharmacokinetics coursework, where understanding why three different BSA formulas exist, and where they diverge, is part of the material.

Researchers normalizing physiological measurements like cardiac output or kidney function across patients of different body sizes, where BSA removes body-size as a confounding variable.

Formula & Methodology

Mosteller (1987):

BSA = √(H × W ÷ 3600)

DuBois & DuBois (1916):

BSA = 0.007184 × W^0.425 × H^0.725

Boyd (1935):

BSA = 0.0003207 × (1000W)^(0.7285 − 0.0188 × log₁₀(1000W)) × H^0.3

Where H = height in cm, W = weight in kg, and BSA comes out in m². Boyd's original formula was derived using weight in grams, which is why the kilogram figure gets multiplied by 1,000 before it goes into the exponent.

Worked example, 70 kg, 170 cm adult:

- Mosteller = √(170 × 70 ÷ 3600) = √3.3056 = 1.818 m²
- DuBois = 0.007184 × 70^0.425 × 170^0.725 = 0.007184 × 6.085 × 41.42 ≈ 1.811 m²
- Boyd = 0.0003207 × 70,000^0.637 × 170^0.3 ≈ 1.836 m²

All three land within about 1.5% of each other, which is typical for an adult of average build. At a dose of 100 mg/m², this patient's Mosteller-based dose would be roughly 182 mg.

How to use this BSA calculator

  1. Enter Body Weight in kg, use current weight, not a target or historical figure, since drug dosing depends on the patient's actual mass right now.
  2. Enter Height in cm, use an actual measured height rather than a self-reported or estimated one.
  3. Read BSA, Mosteller as the default clinical reference figure.
  4. Cross-check against BSA, DuBois and BSA, Boyd if your protocol specifies a particular formula.
  5. Multiply the relevant BSA figure by a drug's dose-per-m² to get the actual dose in mg, if that's what you're calculating this for.

What Insights Does the BSA Calculator Give You?

BSA, Mosteller is the headline output and the figure most oncology software defaults to, it's the number you'd typically reach for first unless a specific protocol says otherwise. BSA, DuBois reflects the original 1916 formula still cited in older protocols and some legacy dosing charts; for patients in a typical adult weight range it tracks Mosteller closely.

BSA, Boyd brings in a weight-adjusted exponent, which makes it worth checking specifically for patients well outside average adult weight, very light, very heavy, or pediatric. Seeing all three side by side is useful precisely because it shows the spread implied by formula choice alone, before any actual biological variation between patients even enters the picture.

Common Mistakes to Avoid

Using outdated weight, a figure from a chart visit weeks or months ago rather than the day of dosing, is the most consequential mistake, since chemotherapy patients frequently lose or gain weight during treatment and BSA needs to track that in real time. A stale weight silently over- or under-doses the patient.

Mixing up which formula a specific protocol requires is another common slip, some older trials and drug labels were calibrated specifically against DuBois, and substituting Mosteller without checking can introduce a small but real discrepancy. And treating BSA as interchangeable with BMI is a conceptual mistake worth avoiding entirely, they answer different questions, and neither substitutes for the other; pair this tool with the BMI Calculator or Ideal Weight Calculator if weight classification, rather than dosing, is actually what you're after.

For general fitness or body composition tracking rather than clinical dosing, the Lean Body Mass Calculator and Body Fat Calculator are the more relevant tools.

Frequently Asked Questions

BSA is the total external surface area of the human body, expressed in square meters. It matters because it accounts for the three-dimensional distribution of body mass in a way that weight alone doesn't, which is why it's the standard basis for dosing many chemotherapy drugs, dosing per m² of BSA predicts drug distribution and effect more reliably than dosing per kilogram of body weight.
Mosteller (1987) is the most widely used in current clinical practice, largely because it's simple and accurate enough for typical adult patients. DuBois (1916) was the original clinical standard for decades, derived from just nine subjects, while Boyd (1935) tends to be preferred for children and patients at extreme weights. For adults of average build, all three usually land within a few percent of each other.
BSA (m²) = √(Height in cm × Weight in kg ÷ 3600). It's just a square root of height times weight divided by 3600, yet it comes within 1-2% of the far more complex DuBois formula for adults in a typical weight range, which is exactly why it became the default in clinical software.
BSA = 0.007184 × Weight^0.425 × Height^0.725, with weight in kg and height in cm. It was the first mathematically derived BSA formula, worked out by Delafield and Eugene DuBois from plaster-cast body measurements of just nine people, and despite that small sample it stayed the clinical reference for over 60 years.
Boyd's formula factors in a weight-dependent exponent, which makes it hold up better across a wider weight range, particularly for very low birth weight infants and patients at the extreme ends of body size. In oncology, it's sometimes chosen over Mosteller specifically for patients well outside typical adult weight.
No, they measure different things entirely. BMI relates weight to height to classify someone as underweight, normal, overweight, or obese, it's a health-risk screening tool. BSA quantifies total body surface for clinical dosing and physiological calculations and doesn't tell you anything about weight status on its own. Use the [BMI Calculator](/bmi-calculator/) for weight classification, and this tool for dosing-related calculations.
BSA shifts with any meaningful weight change, and chemotherapy patients often lose weight from treatment side effects, which lowers their BSA and therefore their weight-appropriate dose. Most oncology protocols recalculate BSA at every treatment cycle for exactly this reason, rather than relying on a single measurement taken at the start.
Yes, burn injuries are classified as a percentage of BSA affected using tools like the Rule of Nines, cardiac index in intensive care is calculated as cardiac output divided by BSA, and pediatric dosing for various non-chemotherapy drugs also uses BSA. Kidney function measurements are sometimes normalized per 1.73 m² of BSA as well.
Each formula was derived from a different sample population using different measurement methods and mathematical approaches, DuBois from plaster casts of nine subjects, Boyd with a weight-dependent exponent, Mosteller as a simplified approximation of DuBois. For most adults of average build the differences are small, typically under 3%, but they can diverge more at unusual heights or weights.
The formulas can technically be applied to children, but accuracy drops meaningfully below roughly 20 kg body weight, where Boyd's formula tends to perform better than Mosteller or DuBois. For pediatric dosing decisions specifically, this should be checked against a pediatric clinical pharmacist rather than relied on alone.
Multiply the drug's prescribed dose per m² by your calculated BSA. If a protocol calls for 75 mg/m² and your BSA works out to 1.8 m², the dose is 75 × 1.8 = 135 mg. Always use the specific formula your protocol or institution specifies, since some drug trials were calibrated using one formula in particular.
Also known as
BSAbody surface areaMosteller formulaDuBois formulaBSA calculator