Printed on 3/17/2026
For informational purposes only. This is not medical advice.
Body surface area (BSA) is a critical measurement in medicine, used to calculate chemotherapy doses, derive cardiac index, and estimate burn severity. This calculator provides results from three validated formulas — Du Bois, Mosteller, and Haycock — allowing clinicians to choose the most appropriate method for their patient population. BSA depends on accurate height and weight — also calculate [BMI Calculator](/tools/bmi-calculator) and [Ideal Weight Calculator](/tools/ideal-weight). BSA is used to normalize cardiac index — assess cardiac risk with [ASCVD Risk Calculator](/tools/ascvd-risk). In oncology patients, monitor renal function for chemotherapy dosing with [eGFR Calculator](/tools/egfr-calculator) or [Creatinine Clearance](/tools/creatinine-clearance) (carboplatin dosing uses Calvert formula with CrCl).
Formula: Du Bois: BSA = 0.007184 × height^0.725 × weight^0.425
Input your height in cm (or feet/inches) and weight in kg (or lbs). Use the unit toggle to switch between metric and imperial measurements.
The calculator computes your BSA using Du Bois (standard), Mosteller (simplified), and Haycock (pediatric-friendly) formulas. Results are shown in square meters (m²).
Use your BSA to calculate drug doses (mg/m²), cardiac index, or burn percentage. Most oncology protocols use the Du Bois or Mosteller formula.
Oncologists & pharmacists
Nearly all cytotoxic chemotherapy protocols dose by BSA (mg/m²). Accurate BSA calculation is critical for efficacy and avoiding toxicity with narrow-therapeutic-index drugs.
Cardiologists & intensivists
Cardiac index (CI = cardiac output ÷ BSA) normalizes heart function for body size. CI helps assess hemodynamic status independent of patient size in ICU and cath lab settings.
Emergency & burn specialists
Burn severity is expressed as percent total body surface area (%TBSA). BSA calculation helps determine fluid resuscitation needs using formulas like Parkland.
Pediatricians & neonatologists
BSA-based dosing is standard in pediatric oncology and some other medications. The Haycock formula is often preferred for infants and children.
Nephrologists
GFR is often indexed to BSA (mL/min/1.73m²) to allow comparison across patients of different sizes. This standardization is essential for CKD staging.
Radiation oncologists
Some radiation dosimetry calculations incorporate BSA when determining treatment fields and doses for certain malignancies.
Most oncology protocols use Du Bois or Mosteller, but some specify one formula. Using the wrong formula can change doses by 5–10%, which matters for narrow-therapeutic-index drugs.
Mosteller formula: BSA = √(height × weight / 3600). It's simpler than Du Bois and produces nearly identical results for most adults — ideal for quick mental math.
The Haycock formula was validated in children and is more accurate at lower heights and weights. Many pediatric oncology centers standardize on Haycock.
Many protocols cap BSA at 2.0 m² for obese patients because drug clearance doesn't scale linearly with body size. Check your specific protocol's guidelines.
For obese patients, some protocols use adjusted body weight (ABW = IBW + 0.4 × (actual − IBW)) instead of actual weight. This prevents overdosing lipophilic drugs.
Self-reported height is often inaccurate (people overestimate). For chemotherapy dosing, measure height with a stadiometer. A 5 cm error changes BSA by ~0.05 m².
Cancer patients often lose or gain weight during treatment. Recalculate BSA at each cycle to avoid under- or overdosing as body composition changes.
A BSA change from 1.75 to 1.85 m² increases a 100 mg/m² dose from 175 mg to 185 mg — a 6% difference. For drugs like doxorubicin with cumulative toxicity, this adds up.
All BSA formulas are mathematical approximations. True body surface area requires 3D scanning. The formulas agree within ~5% for most patients, which is acceptable for clinical use.
When calculating drug doses, note the formula used in the medical record. This ensures consistency if another provider recalculates and enables accurate dose tracking.
This calculator implements the Du Bois (1916), Mosteller (1987), and Haycock (1978) formulas. The Du Bois formula remains the clinical standard referenced in most chemotherapy protocols and drug dosing guidelines. Mosteller's simplified formula was published in the New England Journal of Medicine and is widely used for bedside calculations.
Your BSA is reported in square meters (m²). The average adult BSA is approximately 1.7 m² for women and 1.9 m² for men, though values typically range from 1.5 to 2.2 m². The result itself does not indicate health or disease — it is a physiological parameter used as an input for other clinical calculations.
When BSA is used for drug dosing, the standard dose is typically expressed as mg/m². For example, a chemotherapy dose of 75 mg/m² for a patient with a BSA of 1.8 m² would yield a calculated dose of 135 mg. Small differences in BSA can meaningfully change the final dose, particularly for drugs with narrow therapeutic windows.
BSA is most commonly needed when calculating chemotherapy doses, as nearly all cytotoxic drug protocols are BSA-based. It is also used to derive the cardiac index (cardiac output divided by BSA), which helps assess heart function independent of body size.
Other clinical uses include calculating renal function parameters, estimating fluid requirements, and assessing the extent of burn injuries (where BSA of the burn is expressed as a percentage of total body surface area).
BSA formulas were derived from relatively small, historically non-diverse study populations. The original Du Bois formula (1916) was based on only 9 subjects. While later formulas like Mosteller and Haycock used larger datasets, all are mathematical approximations of a complex three-dimensional measurement.
In obese patients, BSA-based dosing can lead to supratherapeutic drug levels because BSA increases with weight, but drug clearance does not scale proportionally. Many oncology protocols cap BSA at 2.0 m² or use adjusted body weight for very obese patients. Similarly, in cachectic or very small patients, BSA-based doses may need clinical adjustment.
Different formulas can produce slightly different results (typically within 5–10%), which may matter for narrow-therapeutic-index drugs.
For related assessments, see BMI Calculator, Ideal Weight and Creatinine Clearance.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
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