Which BSA formula is most accurate?

The most commonly used formulas and their characteristics: DuBois & DuBois (1916): the historical gold standard, still widely used in clinical practice. Mosteller (1987): simpler calculation, most widely adopted in modern clinical software — BSA = √(height cm × weight kg / 3600). Haycock (1978): most accurate for children. Boyd (1935): most accurate for very obese patients. The differences between formulas are typically under 5% in most adults. No single formula is universally most accurate — Mosteller is preferred for its simplicity and consistent performance across most adult populations.

How is BSA used to calculate chemotherapy doses?

Chemotherapy doses are expressed in mg/m² of BSA — for example, carboplatin at 175 mg/m² BSA. A patient with BSA of 1.8 m² would receive 175 × 1.8 = 315 mg. The rationale for BSA-based dosing is that organ function (particularly liver metabolism and kidney clearance that eliminate drugs) correlates somewhat better with BSA than body weight. However BSA-based chemotherapy dosing has significant limitations: it doesn't account for pharmacogenomic variation, organ dysfunction, or pharmacokinetic factors. Many oncologists now use pharmacokinetically-guided dosing (AUC-based dosing) for drugs like carboplatin.

What is a normal BSA for adults?

Average adult BSA values: men average approximately 1.9 m² (range 1.6-2.3 m²); women average approximately 1.7 m² (range 1.4-2.0 m²). BSA varies significantly with body size — a 6'2" 220 lb man might have BSA of 2.2 m², while a 5'2" 120 lb woman might have BSA of 1.5 m². Children have much smaller BSA proportional to body weight — a 2-year-old averaging approximately 0.52 m². This size difference is why pediatric dosing requires separate BSA calculation and why adult doses are never appropriate for children.

How do burn injuries use BSA calculations?

In burn medicine, BSA is used to estimate the extent of burns using the 'Rule of Nines': head and neck = 9% BSA; each arm = 9% BSA; chest = 9%, abdomen = 9%; upper back = 9%, lower back = 9%; each thigh = 9%, each lower leg = 9%; perineum = 1%. Fluid resuscitation volumes for burn patients (Parkland formula) are calculated as: 4 mL/kg/% burn for the first 24 hours. A 70 kg patient with 30% BSA burns would receive 4 × 70 × 30 = 8,400 mL of Lactated Ringer's in the first 24 hours (half in the first 8 hours, half in the next 16 hours).

Is BSA or BMI more useful for health assessments?

They serve completely different purposes. BMI (weight/height²) is a screening tool for weight-related health risk — associating weight status with disease risk at the population level. BSA (√(height × weight / factor)) estimates total body surface area for clinical procedures and drug dosing. BMI is used in public health, primary care, and nutrition. BSA is used in oncology, cardiology, nephrology, and burn medicine for specific clinical calculations. Neither is better overall — they are tools designed for different applications. Using BSA for health screening or BMI for drug dosing would both be inappropriate misapplications.

How does obesity affect BSA-based drug dosing?

Obesity complicates BSA-based dosing because very high BSA values in obese patients would indicate extremely high absolute drug doses that may not be safe. Most chemotherapy dosing guidelines cap BSA at 2.0-2.2 m² for obese patients or recommend using adjusted ideal body weight rather than actual body weight for BSA calculations. The pharmacokinetics of drugs in obese patients are complex — some drugs distribute into fat (lipophilic drugs) while others don't, and organ function may or may not scale with total body size. Oncologists and pharmacists should consult obesity-specific dosing guidelines for each drug in obese patients.

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Health

Body Surface Area Calculator

Calculate BSA using Mosteller, DuBois, Haycock, and Boyd formulas for drug dosing and clinical applications.

Patient Details

Unit

Weight (lbs)

lbs

Height

Average BSA

1.374

BSA by Formula

Mosteller

1.823 m2

Most used in oncology

DuBois

1.814 m2

Classic, most cited

Haycock

1.831 m2

Best for children

Boyd

0.029 m2

Most complex

Drug Dose Reference (based on avg BSA 1.374 m2)

Dose (mg/m2)	Total Dose (mg)
50 mg/m2	68.7 mg
75 mg/m2	103.1 mg
100 mg/m2	137.4 mg
120 mg/m2	164.9 mg
150 mg/m2	206.1 mg
175 mg/m2	240.5 mg
200 mg/m2	274.8 mg

⚠️ For reference only. Always verify doses with a healthcare provider.

Complete Guide

Body Surface Area Calculator -- Complete USA Guide 2026

The Body Surface Area Calculator provides instant, evidence-based results using clinically validated formulas from leading health organizations. Every calculation runs locally in your browser — no data stored, no account needed, works on any device.

Understanding your body surface area metrics is an important component of proactive health management. This tool gives you the same calculations used in clinical and research settings, with reference ranges and health context that help you understand what your result actually means — and what actionable next steps are appropriate.

Whether you are preparing for a healthcare appointment, tracking progress in a wellness program, or simply curious about this aspect of your health, this calculator provides a reliable, science-backed starting point.

Combine with our BMI Calculator, our TDEE Calculator, and our Calorie Calculator for a comprehensive health assessment.

🔬 How This Calculator Works

BSA is calculated from height and weight using one of four validated formulas. Mosteller: BSA(m²) = √(height(cm) × weight(kg)/3600) — widely used in clinical practice for simplicity. DuBois & DuBois: BSA = 0.20247 × height(m)^0.725 × weight(kg)^0.425 — the historical gold standard, validated against direct measurement of body surface area in 9 subjects in 1916. Haycock: BSA = 0.024265 × height(cm)^0.3964 × weight(kg)^0.5378 — most accurate for pediatric patients. Boyd: mathematically complex but accurate across extreme weight ranges.

BSA in m² is used to normalize drug doses in chemotherapy, cardiac index (cardiac output per m² BSA), and radiation therapy fields.

✅ What You Can Calculate

Evidence-based clinical formulas

Uses peer-reviewed, validated formulas from major health organizations — the same calculations trusted by healthcare professionals in clinical and research settings.

Instant real-time results

Results update as you type — no button to click. Explore multiple scenarios in seconds to understand how changes affect your result.

Complete data privacy

All calculations run entirely in your browser. No personal health data is transmitted, stored, or shared anywhere — ever.

Health context included

Beyond a raw number, results include reference ranges, health category classification, and guidance from major health organizations on what your result means.

Works on all devices

Fully responsive design works perfectly on phone, tablet, and desktop. No app download required — just open in your browser.

Completely free

No signup, no subscription, no premium features. Every calculation and all health context is permanently free for every user.

🎯 Real Scenarios & Use Cases

Annual health monitoring

Calculate and record key health metrics annually to build a personal health history that reveals meaningful trends and supports proactive health decisions over time.

Doctor appointment preparation

Arrive at medical appointments with your own calculations already done, enabling more focused and productive conversations about your health with your healthcare provider.

Wellness program participation

Track progress in employer wellness programs or personal health initiatives with objective, calculated metrics that are meaningful and evidence-based.

Health education and research

Students, educators, and researchers in health and nutrition fields use these tools to apply classroom formulas to real-world calculations and develop genuine health literacy.

💡 Pro Tips for Accurate Results

The clinical application of BSA is primarily for drug dosing — particularly chemotherapy where dosing errors can be life-threatening. If you are calculating BSA for clinical purposes, use the same formula your oncologist or clinical pharmacist is using, since different formulas produce results differing by 3-7%.

For most chemotherapy protocols, Mosteller is the most commonly used formula in the US due to its simplicity and acceptable accuracy. The DuBois formula tends to underestimate BSA in obese patients.

BSA calculation for pediatric patients should use Haycock or Mosteller — the DuBois formula was not validated in children and may be less accurate in this population.

🔢 Data Sources & Methodology

The original DuBois & DuBois paper (1916) measured surface area by covering the bodies of 9 subjects with paper and weighing it — a remarkably simple but effective direct measurement technique that established the reference data for all subsequent regression equations. The resulting formula has been in continuous clinical use for over 100 years despite the small original sample size, a testament to its empirical accuracy.

🏁 Bottom Line

Your body surface area calculation gives you a meaningful, personalized number grounded in validated science — far more useful than generic population guidelines that may not apply to your specific situation, body, and health history.

Use this result as one component of your complete health picture. Combine it with regular monitoring of other key metrics, professional medical guidance when results fall outside normal ranges, and consistent healthy behaviors that address the factors most within your control.

Explore our BMI Calculator, our Body Fat Calculator, our Calorie Calculator, and our TDEE Calculator for a complete health assessment.

Frequently Asked Questions

Body Surface Area (BSA) is the total surface area of the human body in square meters, estimated from height and weight. It is used in medicine primarily for chemotherapy dosing, because many chemotherapy drugs have narrow therapeutic windows — doses too low are ineffective, too high are toxic — and BSA provides a more reliable dose normalization parameter than body weight alone for these drugs. BSA is also used for calculating cardiac output index, burn injury extent assessment, and dosing some biological therapies and blood pressure medications.