Calculate body surface area using Mosteller, Du Bois, Haycock & Gehan-George formulas. Chemotherapy dosing, cardiac index & CKD reference | Calculator4U
Calculate BSA for medical dosing.
The Body Surface Area (BSA) Calculator estimates the total external skin surface of the human body in square meters. This measurement is used extensively in clinical medicine for calculating cytotoxic drug dosages, standardizing metabolic requirements, evaluating burn severity, and normalizing diagnostic indices. BSA provides a more accurate measure of active metabolic size than body weight alone because it accounts for both height and stature, making it superior for standardizing critical treatments across patients of different bodily builds.
BSA is particularly critical in oncology, where most chemotherapy doses are calculated per square meter of body surface area rather than by weight. Cytotoxic chemotherapy drugs have narrow therapeutic windows: the margin between an effective dose and a highly toxic dose is small. Accounting for the relationship between body geometry and drug metabolism helps to ensure maximum therapeutic effectiveness while minimizing life-threatening systemic toxicity. The American Society of Clinical Oncology (ASCO), National Cancer Institute (NCI), and Hematology/Oncology Pharmacy Association (HOPA) all specify BSA-based dosing as the clinical standard for most cytotoxic regimens.
Multiple scientific formulas exist for calculating BSA, with the Du Bois and Mosteller formulas being most widely cited. While the original Du Bois equation remains a historic benchmark, the modern Mosteller formula is frequently preferred in clinical practice for its mathematical simplicity while maintaining a strict margin of accuracy. The average adult BSA ranges from 1.7 to 1.9 m², with men typically exhibiting a larger baseline area than women. Extremes of height or weight require precise formula considerations in active clinical settings.
Each validated formula utilizes height (H) in centimeters and weight (W) in kilograms to output total surface area in square meters (m²):
| Formula | Equation | Year | Clinical Indication / Best For |
|---|---|---|---|
| Mosteller | √[(H × W) / 3600] | 1987 | Standard US clinical practice; simplest to calculate; within 2% of Du Bois. |
| Du Bois | 0.007184 × H^0.725 × W^0.425 | 1916 | Original formula; most heavily cited in medical literature; standard research protocol. |
| Haycock | 0.024265 × H^0.3964 × W^0.5378 | 1978 | Pediatric patients (neonates to adolescents); most accurate for children. |
| Gehan-George | 0.0235 × H^0.42246 × W^0.51456 | 1970 | Oncology protocols specifying this dataset; derived strictly from 401 cancer patients. |
| Boyd | 0.0003207 × H^0.3 × W^(0.7285−0.0188·log₁₀W) | 1935 | Neonates, infants, and patients presenting with extreme or unusual body habitus. |
Note: For most typical adults, all five formulas cross-agree within a 5% margin. Discrepancies become clinically pronounced only at extreme physiological outliers of height and weight.
Standard cytotoxic drugs calculate their absolute absolute mass allocation through a strict surface ratio profile:
Practical Example: A patient measuring 170 cm in height and weighing 70 kg yields a Mosteller calculation of: √[(170 × 70) ÷ 3600] = √3.3055 = 1.82 m² BSA. If the oncologist prescribes a chemotherapy agent at a baseline index of 25 mg/m², the final dose configuration equals: 1.82 m² × 25 mg/m² = 45.5 mg. Standard clinical guidelines allow a ±10% rounding variance to match commercial vial quantities without altering core therapeutic outcomes.
Carboplatin stands as the most critical exception to traditional BSA-based drug calculation protocols within modern oncology. The physical clearing mechanism of carboplatin correlates directly with the patient's glomerular filtration rate (GFR) rather than aggregate skin surface area. Using a standard BSA matrix to calculate carboplatin will cause highly inaccurate and potentially dangerous toxic dosing. Instead, clinicians must calculate dosing using the Calvert Formula:
The target Area Under the Curve (AUC) typically spans a value index of 5–7 mg·min/mL for primary first-line therapeutic treatments.
Historically, many medical centers implemented a strict structural ceiling that capped calculated BSA inputs at a maximum of 2.0 m² for obese individuals to avoid perceived over-dosing errors. However, current clinical safety standards recommend against routine empirical BSA capping. Peer-reviewed oncology studies demonstrate that arbitrary capping induces systematic under-dosing in high-BMI cohorts, significantly reducing tumor clearing efficacy and worsening survival outcomes. Dosage modifications should be handled on an individualized, case-by-case basis under the explicit advisory of a specialized oncology clinical pharmacist.
| Population Segment | Typical BSA (m²) | Clinical Reference Notes |
|---|---|---|
| Newborn | 0.20 – 0.25 | Utilize Haycock equations; requires highly specialized neonatal metabolic protocols. |
| Infant (1 Year) | ~0.50 | Haycock formulas remain the preferred clinical estimation path. |
| Child (5 Years) | 0.70 – 0.80 | Pediatric oncology standard tracking; requires age-adjusted metrics. |
| Child (10 Years) | ~1.14 | Approaching standard adolescent ranges (1.40 – 1.70 m²). |
| Adult Female | 1.60 – 1.80 | Standard reference profile; approaches the global GFR baseline constant of 1.73 m². |
| Adult Male | 1.80 – 2.00 | Standard reference adult masculine scale. |
| Large Adult | 2.00 – 2.50 | Requires clear monitoring profiles; evaluate dose-capping limitations relative to therapy types. |
Clinical Disclaimer: This electronic assessment asset is developed exclusively for baseline educational and informational reference applications. All patient-facing chemotherapy and drug volume calibrations must be fully verified against active institutional medical guidelines and original manufacturing package inserts by a licensed oncologist and registered clinical pharmacist. Never make solo diagnostic or point-of-care patient management interventions based on automated web outputs.
BSA (m²) = √[(Height cm × Weight kg) / 3600]. N Engl J Med 1987;317:1098. Most widely used in US clinical practice. Within 2% of Du Bois method. 170 cm, 70 kg → √[(170×70)/3600] = √3.306 = 1.82 m². Imperial: convert inches × 2.54 = cm; lb ÷ 2.205 = kg first.
Males: 1.8–2.0 m². Females: 1.6–1.8 m². Nephrology reference: 1.73 m² (eGFR normalization standard for CKD-EPI/MDRD). Range: 1.5 m² (small female) to 2.5 m² (large male). Newborn: 0.20–0.25 m². Age 10: ~1.14 m². BSA is a size parameter, not a health indicator.
Cytotoxic drugs have narrow therapeutic windows. BSA correlates better with drug metabolism and clearance than weight alone (accounts for both height + weight = better proxy for metabolic mass). Standard for ASCO/NCI/HOPA: anthracyclines, taxanes, vinca alkaloids, platinum agents. Exception: carboplatin — use Calvert AUC formula, never BSA.
Haycock formula: BSA = 0.024265 × H^0.3964 × W^0.5378. Validated neonates to adults; accounts for proportionally larger head and different limb ratios in children. De facto US pediatric oncology and pharmacy standard. Haycock and Mosteller agree within 2% for standard-weight adults — use Haycock for any patient under 18 or with low body weight.
Carboplatin clears renally — use Calvert, not BSA. Calvert formula: Dose (mg) = Target AUC × (CrCl + 25). Target AUC: 5–6 mg·min/mL (first-line); 2–3 (retreatment/combination). Using BSA for carboplatin = inaccurate exposure, documented oncology medication error source. This exception applies to carboplatin only — all other platinum agents (cisplatin, oxaliplatin) use BSA.
No — ASCO/HOPA (2012, reaffirmed 2025) recommend against routine capping. Studies showed capping causes systematic underdosing in obese patients, potentially reducing efficacy and worsening survival. Dose adjustments should be individualized by drug, toxicity profile, and organ function — not automatically applied at a BSA threshold. Follow your institution's current oncology protocol.
CI (L/min/m²) = Cardiac Output (L/min) ÷ BSA (m²). Normal: 2.5–4.0 L/min/m². Normalizes heart function for body size — standard in ICU, cardiac cath lab, heart failure assessment, cardiac surgery. CI <2.0 = cardiogenic shock. CI >4.0 = hyperdynamic state (sepsis, pregnancy). Without BSA normalization, raw cardiac output is misleading across patients of different sizes.