Body Surface Area Calculator — BSA Formula

Body Weight

10200

Height

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?

A body surface area (BSA) calculator computes the total external surface of the human body in square metres (m²) using your weight and height. BSA is a fundamental clinical measurement used primarily in oncology for chemotherapy drug dosing, in burns medicine for injury classification, and in critical care for normalising cardiac output and kidney function measurements.

This calculator implements all three major BSA formulas:

Mosteller (1987) — the simplest and most widely used in current oncology protocols
DuBois & DuBois (1916) — the original clinical standard, used in older protocols
Boyd (1935) — preferred for patients at extreme weights, including paediatric oncology

For most adult patients, the three formulas agree within 2–5% — the Mosteller result is highlighted as the primary output since it is the current clinical default in most Indian and international oncology centres.

How to use this BSA calculator

Enter Body Weight in kg — use current weight, not ideal weight. In oncology, weight should be re-measured at each treatment cycle as it can change significantly.
Enter Height in cm — height is typically constant for adults. Use actual measured height, not self-reported.
Read BSA — Mosteller as the primary value for modern oncology dosing. Cross-check with DuBois if the protocol specifies the DuBois formula.
Multiply by the drug's dose per m² to get the actual dose in mg. For example: if dose is 75 mg/m² and BSA is 1.68 m², actual dose = 75 × 1.68 = 126 mg.

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 × W^(0.7285 − 0.0188 × log₁₀(W)) × H^0.3

Where H = height (cm), W = weight (kg), BSA in m²

Worked example:

Adult male, 72 kg, 174 cm.

- Mosteller = √(174 × 72 ÷ 3600) = √(3.48) = 1.866 m²
- DuBois = 0.007184 × 72^0.425 × 174^0.725 = 0.007184 × 7.534 × 52.47 = **2.840... **

Wait, let me recalculate: 0.007184 × 72^0.425 × 174^0.725

72^0.425: ln(72)×0.425 = 4.277×0.425 = 1.818, e^1.818 = 6.16
174^0.725: ln(174)×0.725 = 5.159×0.725 = 3.740, e^3.740 = 42.17

DuBois = 0.007184 × 6.16 × 42.17 = 0.007184 × 259.8 ≈ 1.867 m²

- Mosteller = 1.866 m²
- DuBois ≈ 1.867 m²

Both formulas give essentially the same result for this patient — typical for adults in the normal weight range. For a drug dosed at 100 mg/m², this patient would receive approximately 187 mg.

Assumptions: All three formulas were derived from adult populations and are most reliable for patients with BMI 18.5–35 and heights above 150 cm. The Mosteller formula is less accurate at extreme weights (< 30 kg or > 100 kg). For paediatric dosing, consult a paediatric clinical pharmacist — BSA formula accuracy varies significantly below 20 kg. For non-clinical applications like general fitness tracking, use the Lean Body Mass Calculator and Body Fat Calculator instead.

Frequently Asked Questions

What is body surface area (BSA)?

Body Surface Area (BSA) is the total surface area of the human body, measured in square metres (m²). Unlike body weight or BMI, BSA accounts for the three-dimensional distribution of body mass and is used in medicine as a more reliable basis for drug dosing, particularly for chemotherapy agents, where dosing per m² of BSA is more predictive of drug distribution and effect than dosing per kg of body weight alone.

Which BSA formula is most accurate?

The Mosteller formula (1987) is currently the most widely used in clinical practice due to its simplicity and good accuracy. The DuBois and DuBois formula (1916) was the original reference for decades but was derived from only nine subjects. The Boyd formula (1935) is considered more accurate for children and patients at extreme weights. For adults of average weight, all three formulas typically agree within 5% of each other.

What is the average BSA for Indian adults?

The average BSA for Indian adults is approximately 1.60–1.70 m² for males and 1.45–1.55 m² for females, which is slightly lower than the Western reference of 1.73 m² (DuBois reference man) due to differences in average height and weight. This is clinically relevant because Indian patients receiving chemotherapy doses calibrated to a 1.73 m² reference may receive proportionally higher doses per kg than intended if BSA is not calculated from actual measurements.

How is BSA used in cancer treatment in India?

BSA-based dosing is standard for nearly all cytotoxic chemotherapy drugs administered in Indian oncology — including 5-fluorouracil, cisplatin, carboplatin, and doxorubicin. Oncologists calculate each patient's BSA from their current weight and height, then multiply the drug's dose per m² by the patient's BSA to get the exact dose in mg or mg/m². Recalculating BSA at each cycle captures weight changes during treatment.

What is a normal BSA for an adult?

For adults, a BSA of 1.6–2.0 m² is typical. The classic reference values from DuBois (1916) are 1.73 m² for an average male and 1.60 m² for an average female — these are based on Western populations. Indian adults of average height (165–170 cm males, 152–158 cm females) typically have BSA values of 1.65–1.80 m² (males) and 1.45–1.60 m² (females) depending on weight.

What is the Mosteller formula for BSA?

The Mosteller formula (1987) is: BSA (m²) = √(Height (cm) × Weight (kg) ÷ 3600). It is remarkably simple — just a square root of height times weight divided by 3600 — yet produces results within 1–2% of the more complex DuBois formula for adults in the typical weight range. Its simplicity made it the preferred formula in clinical software and oncology protocols worldwide.

What is the DuBois formula for BSA?

The DuBois and DuBois formula (1916) is: BSA = 0.007184 × Weight^0.425 × Height^0.725. It was the first mathematically derived BSA formula, established by Delafield DuBois and Eugene DuBois using plaster-cast measurements of nine subjects. Despite its small derivation sample, it remained the clinical standard for over 60 years. It is still widely cited and used in older oncology protocols.

What is the Boyd formula for BSA?

The Boyd formula (1935) is: BSA = 0.0003207 × Weight^(0.7285 − 0.0188 × log₁₀(Weight)) × Height^0.3. It includes a weight-dependent exponent, making it more accurate across a wider range of patient weights — particularly for very low birth weight infants, paediatric patients, and extremely obese adults. In oncology, it is sometimes preferred over Mosteller for patients outside the typical adult weight range.

Is BSA used in India for any purpose other than chemotherapy?

Yes. Beyond oncology drug dosing, BSA is used in India for: burn assessment (burns are classified as percentage of BSA using the Rule of Nines); paediatric drug dosing for many non-chemotherapy drugs; cardiac index calculation (cardiac output ÷ BSA, used in ICU monitoring); and research studies comparing physiological parameters across populations of different sizes. It is also used in renal function assessment — glomerular filtration rate is sometimes normalised per 1.73 m² of BSA.

Can BSA replace BMI for health assessment?

No — BSA and BMI serve different purposes. BMI assesses weight relative to height to classify underweight, normal, overweight, or obese status. BSA quantifies total body surface area for dosing and physiological calculations. BSA does not diagnose obesity or assess health risk in the way BMI does. Use BSA for clinical drug dosing and medical calculations; use [BMI Calculator](/bmi-calculator/) for weight classification and health risk assessment.

How does weight change affect BSA and drug dosing?

BSA changes with every significant weight gain or loss. During chemotherapy, patients often lose weight due to side effects — reducing their BSA and therefore their weight-appropriate drug dose. Most oncology protocols recalculate BSA at every cycle to adjust doses accordingly. A 5 kg weight loss in a 70 kg patient reduces Mosteller BSA by approximately 0.03–0.04 m², which on a dose of 100 mg/m² represents a dose reduction of 3–4 mg per cycle.