Which formula should I use — Mosteller or Du Bois?

Use the formula specified in the chemotherapy protocol. If not specified, Mosteller is preferred for most clinical applications due to simplicity and comparable accuracy. Some older protocols specifically require Du Bois.

Should I use actual weight or ideal weight for BSA in chemotherapy?

Most oncology dosing uses actual body weight for BSA calculation. Unlike Cockcroft-Gault renal dosing, there is no standard adjustment to IBW for BSA. However, many centres cap BSA at 2.0 m² for obese patients in initial cycles — check your institutional policy.

How does BSA relate to carboplatin dosing?

Carboplatin is dosed using the Calvert formula (Dose = AUC × [GFR + 25]) not BSA directly. BSA is still needed for other agents in the same regimen. eGFR from the lab (not Cockcroft-Gault) is typically used in the Calvert formula.

Body Surface Area (BSA) — Free Pharmacy Calculator

🎯

Oncology patient starting carboplatin. The dose is 5 mg/mL/min (AUC 5) and you need to calculate the AUC dose using Calvert's formula — first step is BSA, then GFR.

Body Surface Area (BSA)

Clinical

Weight (kg)

Imperial mode auto-converts lb→kg

Height (cm)

Imperial: enter inches

Formula

Mosteller: √(H × W ÷ 3600) Du Bois: 0.007184 × H⁰·⁷²⁵ × W⁰·⁴²⁵ Haycock: 0.024265 × H⁰·³⁹⁶⁴ × W⁰·⁵³⁷⁸ Average adult BSA ≈ 1.7–1.8 m²
Mosteller is recommended for most clinical use. Haycock is preferred for neonates and children.

Reference: Mosteller RD — NEJM 1987 · Haycock GB et al. — J Pediatr 1978

⚕️ Clinical safety: 🇦🇺 Verify with facility drug formulary and senior clinician · Meets AHPRA/ACSQHC standards

1 What this calculator does

Calculates body surface area (BSA) in m² using Mosteller and/or Du Bois formulas. BSA is used for chemotherapy dosing, high-alert medication calculation, and paediatric drug dosing where weight-based dosing is insufficient.

2 Formula & professional reasoning

Mosteller: BSA = √(Height(cm) × Weight(kg) / 3600)
Du Bois: BSA = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425

The Mosteller formula is simpler and gives results within 2% of Du Bois for most adults — preferred for most clinical applications. The Du Bois formula is the original 1916 derivation and is used in some oncology protocols that specify it. Both are provided for completeness. BSA in m² is used because chemotherapy dosing in mg/m² was historically calibrated from body size studies using BSA as the normalisation factor.

3 Worked examples

⚠️ Illustrative example only — not clinical or professional instruction.

Basic

Average adult male

Given: Height 175 cm, Weight 75 kg

Working: Mosteller: √(175 × 75 / 3600) = √(3.646)

Answer: BSA 1.91 m²

💡 Normal adult BSA range: 1.6–2.0 m² for women, 1.7–2.2 m² for men.

Standard

Adult female oncology patient

Given: Height 162 cm, Weight 68 kg

Working: Mosteller: √(162 × 68 / 3600) = √(3.06)

Answer: BSA 1.75 m²

💡 If carboplatin dose = AUC 5, use Calvert formula: Dose = 5 × (GFR + 25) — BSA not used for carboplatin but required for most other chemotherapy agents.

Advanced

Obese patient — capping controversy

Given: Height 168 cm, Weight 120 kg

Working: Mosteller: √(168 × 120 / 3600) = √(5.6)

Answer: BSA 2.37 m²

💡 Many oncology centres cap BSA at 2.0 m² for initial cycles in obese patients — check your institutional protocol before dosing.

4 Sanity check

Normal adult BSA range

1.6–2.2 m²

Results outside 1.4–2.5 m² should prompt weight and height verification.

Paediatric BSA

Neonate: 0.2 m² · Child 10 kg: 0.5 m² · Adolescent: 1.4 m²

Paediatric oncology protocols often use both mg/kg and mg/m² — check protocol specifically.

BSA capping

Many centres cap at 2.0 m² for obese patients

Always check your institution's oncology protocol for BSA capping policy before calculating dose.

Weight to use

Actual body weight for most chemotherapy

Unlike Cockcroft-Gault, BSA for chemotherapy generally uses ACTUAL body weight — verify with your oncology pharmacist.

5 Common errors

Error	Cause	Consequence	Fix
Using incorrect formula for the protocol	Assuming Mosteller and Du Bois are interchangeable	Dose difference of 2–5% — small but significant for narrow therapeutic index drugs	Check the specific protocol — some oncology regimens mandate Du Bois formula. Use whatever the protocol specifies.
Using ideal weight instead of actual	Confusion with Cockcroft-Gault habit	Under-dosing chemotherapy in obese patients (unless capping applies)	For most chemotherapy BSA calculations, use ACTUAL body weight. Exception: if protocol mandates adjusted or ideal weight.
Not verifying height and weight independently	Using patient-reported values	BSA error propagated through entire chemotherapy dose	Weigh and measure the patient — particularly important at start of new chemotherapy cycle
Re-using BSA from previous cycle without rechecking weight	Time saving	Significant weight change (common during chemotherapy) not reflected in dose	Re-calculate BSA at start of each chemotherapy cycle using current height and weight