Body Surface Area (BSA) Calculator
Calculate BSA using common clinical formulas (Mosteller, DuBois, Haycock, Gehan & George) with clear working, dosing context, practice questions, FAQs, and references.
Tip: commas are allowed (e.g. 1,000).
Educational use only. Always follow local policy for dosing and verify calculations in clinical context.
How it works
Body Surface Area (BSA) is an estimate of the body’s external surface area and is expressed in square meters (m²). In healthcare, BSA is frequently used to scale doses—especially chemotherapy regimens prescribed as mg/m²—and to index certain physiological measurements (for example, cardiac index).
Because directly measuring surface area is impractical, BSA is calculated from height and weight using validated equations. Different formulas were derived from different datasets and methods, so outputs can vary slightly. Those differences are usually small, but they can matter when protocols include dose rounding rules or BSA caps—so always follow your local protocol.
Common clinical uses
- Chemotherapy dosing (mg/m² → mg)
- Indexing cardiac output (cardiac index)
- Some high-risk or narrow-therapeutic medications (protocol dependent)
- Research/physiology calculations where body size scaling is needed
Formula
How to apply BSA to a prescribed dose (mg/m²)
If a regimen dose is prescribed as mg/m², the total dose is typically calculated as:
After calculation, protocols often apply rounding rules (e.g., vial sizes) and may include additional clinical constraints (renal/hepatic function, intent of treatment, toxicity history).
Worked examples
Example 1 (Mosteller): Height 170 cm, weight 70 kg
Answer: 1.82 m²
Example 2 (Mosteller): Height 160 cm, weight 55 kg
Answer: 1.56 m²
Example 3 (DuBois): Height 180 cm, weight 90 kg
Answer: 2.11 m²
Practice questions
Designed for student nurses, junior doctors, and pharmacists who want to verify their steps.
Try it first, then reveal the answer and working.
Practice 1: Height 170 cm, weight 70 kg. What is BSA (Mosteller)?
Show answer + working
Answer: 1.82 m²
Practice 2: Height 165 cm, weight 95 kg. What is BSA (Mosteller)?
Show answer + working
Answer: 2.09 m²
Practice 3: Height 110 cm, weight 18 kg. What is BSA (Mosteller)?
Show answer + working
Answer: 0.74 m²
Clinical notes
Dose rounding and capped BSA
Many chemotherapy protocols include dose rounding (e.g., vial-size practicality) and may include rules for capped BSA in selected regimens. These policies are protocol-specific and vary by institution, drug, and treatment intent.
If you are calculating chemotherapy doses, use your local regimen reference and pharmacist guidance for rounding thresholds, maximum doses, capped BSA rules, and adjustments for toxicity or organ function.
Obesity and dosing considerations
BSA-based dosing in obesity can be complex and may involve protocol-specific guidance, clinical judgement, and pharmacist oversight. Some regimens specify full weight-based BSA, while others define alternative approaches depending on the drug and indication.
Don’t substitute IBW/AdjBW into a BSA equation unless your protocol explicitly directs you to do so.
Pediatrics
Some formulas (e.g., Haycock) are frequently cited in pediatric contexts, but the correct approach depends on your pediatric oncology or pharmacy protocol. Always use the regimen’s specified method and rounding policy.
Clinical safety note: BSA is an estimate used in dosing and indexing. If you are using BSA to calculate medication doses (especially chemotherapy), always follow your local protocol for the required formula, rounding rules, and any caps or dose limits. Confirm units and seek pharmacist/oncologist guidance when unsure.
Related calculators
Frequently asked questions
Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.
References & Sources
Key publications (original formula sources)
Mosteller RD — Simplified calculation of body-surface area
PubMedN Engl J Med (1987)
Classic simplified formula widely adopted in clinical calculators and dosing workflows.
Du Bois D & Du Bois EF — A formula to estimate surface area from height and weight
JournalArch Intern Med (1916)
Historic BSA equation still referenced by many systems and tools.
Haycock GB, Schwartz GJ, Wisotsky DH — Height–weight formula validated across ages
PubMedJ Pediatr (1978)
Validated BSA equation commonly referenced in pediatric and general contexts.
Gehan EA, George SL — Estimation of human body surface area from height and weight
SummaryCancer Chemother Rep (1970)
Alternative validated BSA approach used in some calculators.
Clinical tools & protocol-style resources
eviQ — Body Surface Area (BSA) calculator
ProtocoleviQ (Cancer Institute NSW)
Protocol-style calculator resource with references and version history (widely used in AU oncology).
Medscape — Body Surface Area Based Dosing
ClinicalMedscape / QxMD tool
Clinical tool summary for BSA-based dosing (commonly cites Mosteller).
Calculator.net — Body Surface Area Calculator
ReferenceCalculator.net
Example of how common tools present multiple BSA formulas and background context.
References are provided for education and transparency. For clinical dosing decisions—especially chemotherapy—always follow your local protocol and pharmacist/oncologist guidance.