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APLS age-based weight estimate (pediatric)

Age in years (a 6-month-old is 0.5). Also accepts months or days. The formula band is chosen from age: under 1 year, 1–5 years, or 6–12 years. Outside 0–12 years there is no APLS age-based formula.

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

Estimated body weight in kilograms, chosen by age band. Under 1 year: weight = 0.5 × age in months + 4 (equivalently 6 × age in years + 4). 1–5 years: weight = 2 × age in years + 8. 6–12 years: weight = 3 × age in years + 7 (Luscombe & Owens). Age in years is taken at the last birthday (whole years) for the two child bands. This is a population point estimate for use only when a measured weight cannot be obtained — a directly measured weight is always preferred, and a Broselow length tape is a length-based alternative. Not defined below 0 or above 12 years.

Limitations and notes

An ESTIMATE, not a measurement or severity score — interpretation is intentionally empty (research: no clinical interpretation/risk bands; the only bands are the age bands that select the formula). A directly measured weight is always preferred; use the estimate only when weighing is impossible. The Broselow length tape (Lubitz 1988, PMID 3377285) is a length-based alternative but needs the physical tape and the child supine, and loses accuracy above ~25 kg. The updated 1–5y band (2×age)+8 is algebraically identical to the legacy APLS (age+4)×2; only the 6–12y band was steepened to (3×age)+7 (Luscombe & Owens 2007, PMID 17213259) because the legacy formula underestimated measured weight by a mean of 18.8% across ages 1–10y — e.g. at 10y the legacy 28 kg vs updated 37 kg (~24% gap). Population-derived formulas carry substantial individual error and systematically UNDERESTIMATE in overweight/obese children; validated range is 0–12 years (do not extrapolate to neonates outside term ranges, adolescents >12y, or adults). Age-unit trap: the infant formula is in months, the child formulas in whole years; this calculator takes a single age input and converts internally. No research values were left unsourced (no [NEEDS SOURCE] carried); the 0–12 year input bounds are engineering input-validity limits, not cited clinical thresholds.

Accepted input ranges

  • Age — 0–12 years

References

  1. Luscombe M, Owens B. Weight estimation in resuscitation: is the current formula still valid? Arch Dis Child. 2007;92(5):412–415.PMID 17213259DOI 10.1136/adc.2006.107284
  2. Advanced Life Support Group. Advanced Paediatric Life Support: The Practical Approach. 5th ed. Wiley-Blackwell; 2011. ISBN 978-1-4443-3059-5.Source
  3. Kelly A-M, Nguyen K, Krieser D. Validation of the Luscombe weight formula for estimating children's weight. Emerg Med Australas. 2011;23(1):59–62.PMID 21134132DOI 10.1111/j.1742-6723.2010.01351.x
  4. Lubitz DS, Seidel JS, Chameides L, et al. A rapid method for estimating weight and resuscitation drug dosages from length in the pediatric age group. Ann Emerg Med. 1988;17(6):576–581.PMID 3377285

Version and changelog

v1.0.0 · General

  • 2026-07-25 v1.0.0 — Initial release: APLS updated three-band age-based weight estimate (infant/1–5y/6–12y).

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.