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Body surface area (Mosteller)

Body length / height. Accepts centimetres (default), inches, or metres.

Body weight. Accepts kilograms (default), pounds, or grams.

Independent clinical validation: pending

Two independent clinical validators will be named here once review is complete.

Validator slot open 1
Validator slot open 2

How it is calculated

Body surface area is estimated with the Mosteller (1987) formula: BSA in square metres = the square root of (height in cm × weight in kg ÷ 3600), which is equivalently √(height × weight) ÷ 60. It is a single closed-form expression with no age or sex terms and no interpretation bands. The result is a body-size scalar used as a denominator elsewhere — e.g. drug dosing per m² (mg/m²) and indexed haemodynamic/renal parameters such as cardiac index (L/min/m²). Compute in full floating point and round once at display (precision 2); do not chain rounded intermediates.

Limitations and notes

No interpretation bands: BSA is a continuous body-size scalar with no published cut-point that stratifies patients, so interpretation is intentionally empty — present the value as a derived body-size estimate and defer any dosing/indexing interpretation to the downstream calculation that consumes it. Estimate only, not a clinical device: Mosteller was validated only against the Du Bois formula (itself fit to 9 adults in 1916), not against direct surface-area measurement; agreement with pediatric-fit estimators (Haycock, Gehan-George) is close but widens at the extremes (neonates, severe obesity), so a platform indexing by BSA should record which formula it uses. The main failure mode is unit transposition (lb↔kg, in↔cm): because BSA scales as sqrt(h·w) a swapped unit yields a wrong-but-plausible number the formula cannot self-detect — unit labels and the range checks are the defense. The height (~30–220 cm) and weight (~0.3–250 kg) bounds are input-validity limits chosen to span the PICU range, NOT clinical limits and not from Mosteller 1987. NEEDS SOURCE (carried from research): a specific head-to-head pediatric accuracy figure vs Haycock/Gehan-George is not asserted here, and any protocol BSA cap for dosing (commonly cited around 2.0–2.2 m²) is a protocol overlay, not part of Mosteller, and lacks a primary numeric source.

Accepted input ranges

  • Height — 30–220 cm
  • Weight — 0.3–250 kg

References

  1. Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098.PMID 3657876DOI 10.1056/NEJM198710223171717
  2. Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17(6):863–871. (Reprinted: Nutrition. 1989;5(5):303–311.)PMID 2520314
  3. Evidencio — Body surface area (Mosteller formula), model 518.Source
  4. Omnicalculator — BSA Calculator (Body Surface Area).Source

Version and changelog

v1.0.0 · General

  • 2026-07-25 v1.0.0 — Initial release: Mosteller body surface area from height and weight.

Important

For use by qualified health professionals as an informational and educational aid. It supports clinical judgment and does not replace it. Verify every result independently before making a clinical decision. This is not a medical device.