Pediatric Weight Formula Calculator – APLS & Luscombe–Owens
Compare historical revised APLS and Luscombe–Owens pediatric weight formulas by completed age, with exact substitutions, age boundaries, and current limitations.
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About
Formula
Interpretation
How this pediatric weight formula calculator works
Enter completed age at the last birthday. For ages 1–5, the calculator shows revised APLS (2 × age + 8 kg) and Luscombe–Owens (3 × age + 7 kg) as separate historical estimates. For ages 6–12, both sources use the same 3 × age + 7 arithmetic, so one value is shown with both formula identities. Age 13 is supported by Luscombe–Owens only. No fractional age is rounded into the calculation. [5, 6, 7]
Pediatric weight formulas by completed age
- Completed age
- 1–5 years
- Revised APLS
- 2 × age + 8 kg
- Luscombe–Owens
- 3 × age + 7 kg
- This calculator
- Shows both
- Completed age
- 6–12 years
- Revised APLS
- 3 × age + 7 kg
- Luscombe–Owens
- 3 × age + 7 kg
- This calculator
- Shows one value and identifies both formula sources
- Completed age
- 13 years
- Revised APLS
- Not included in the 6–12 branch
- Luscombe–Owens
- 3 × age + 7 kg
- This calculator
- Luscombe–Owens only
These are historical completed-age formulas expressed in kilograms. They are not measured weights or current universal recommendations. [5, 6]
Why do APLS pediatric weight formulas differ online?
Different historical APLS versions and age branches use different expressions. For ages 1–5, (age + 4) × 2 and 2 × age + 8 are algebraically equivalent. The revised APLS 6–12-year branch uses 3 × age + 7, the same arithmetic as Luscombe–Owens in that age range. This page implements only the two locked historical methods shown above; it does not imply that every APLS version is identical. [5, 6, 7]
Which weight source is preferred today?
Current guidance generally favors a measured or reliable recent or caregiver-reported weight. When those are unavailable, an appropriate length-based method is often more accurate than a simple age formula, especially when body habitus is considered. Historical age-only formulas remain transparent legacy or reference estimates where a local workflow still names them; this is not a universal four-step hierarchy. [1, 2, 3, 4, 11]
How accurate are age-based pediatric weight formulas?
Age alone cannot represent height or body habitus. Systematic reviews report low overall accuracy for age formulas, without supporting one universal accuracy percentage. They may underestimate actual weight where obesity is more common and overestimate it where malnutrition is more common. Country, population, era, illness, and clinical setting affect performance; no age formula verifies an individual child's true weight. [3, 4, 8]
Age-based estimate vs pediatric IBW, BMI and growth percentiles
This page uses completed age only to reproduce historical emergency weight estimates. It is not a pediatric ideal body weight or adjusted body weight method, weight-for-height assessment, BMI or BMI-for-age calculator, weight-for-age percentile, healthy-weight assessment, or growth chart. This is not a growth-chart or percentile calculator. Those tasks require measured anthropometrics, age- and sex-specific growth references, or another appropriate specialized method. [9, 10]
Medication and resuscitation boundaries
Historical weight estimates have been used in emergency workflows, but this page does not generate a medication dose, fluid volume, equipment size, defibrillation energy, or other treatment setting. AHA/AAP guidance recommends using body weight for pediatric resuscitation medication arithmetic without exceeding recommended adult doses; the applicable clinical workflow and independent verification remain separate from this calculator. [1, 2, 11]
Supported ages and limitations
This calculator accepts completed whole ages 1–13. It does not support months, fractional years, infants under 1 year, or ages over 13. Obesity, malnutrition, chronic illness, edema, major fluid shifts, amputation, and unusual body habitus can materially separate an age estimate from measured weight. No result is an individual measurement, diagnosis, treatment target, or proof of an appropriate dosing weight.
References
- American Heart Association and American Academy of Pediatrics. Part 8: Pediatric Advanced Life Support: 2025 Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Pediatrics. 2026;157(1):e2025074351.
- Djakow J, et al. European Resuscitation Council Guidelines 2025: Paediatric Life Support. Resuscitation. 2025;215(Suppl 1):110767. DOI 10.1016/j.resuscitation.2025.110767.
- Young KD, Korotzer NC. Weight Estimation Methods in Children: A Systematic Review. Ann Emerg Med. 2016;68(4):441–451.e10. PMID 27105839. DOI 10.1016/j.annemergmed.2016.02.043.
- Wells M, Goldstein LN, Bentley A. The accuracy of emergency weight estimation systems in children: a systematic review and meta-analysis. Int J Emerg Med. 2017;10:29. PMID 28936627. PMCID PMC5608658. DOI 10.1186/s12245-017-0156-5.
- Luscombe MD, Owens BD, Burke D. Weight estimation in paediatrics: a comparison of the APLS formula and the formula Weight = 3(age) + 7. Emerg Med J. 2011;28(7):590–593. PMID 20659877. DOI 10.1136/emj.2009.087288.
- Seddon C, Lockitt L, Dhanjal S, Eisenhut M. Validation of Advanced Paediatric Life Support Formulas for Weight Calculation in a Multiethnic Population. ISRN Pediatr. 2012;2012:869634. PMID 23050162. PMCID PMC3463167. DOI 10.5402/2012/869634.
- Flannigan C, et al. Are APLS formulae for estimating weight appropriate for use in children admitted to PICU? Resuscitation. 2014;85(7):927–931. PMID 24727134. DOI 10.1016/j.resuscitation.2014.03.313.
- Wells M, Goldstein LN. The utility of pediatric age-based weight estimation formulas for emergency drug dose calculations in obese children. J Am Coll Emerg Physicians Open. 2020;1(5):947–954. PMID 33145545. PMCID PMC7593471. DOI 10.1002/emp2.12099.
- World Health Organization. WHO Child Growth Standards: Weight-for-age.
- Centers for Disease Control and Prevention. What Growth Charts Are Recommended?
- Resuscitation Council UK. Paediatric Life Support Guidelines. 2025. Weight and drug dosing in resuscitation.
FAQ
It reproduces two historical population-derived formulas: revised APLS uses weight (kg) = 2 × completed age + 8 for ages 1–5 and 3 × completed age + 7 for ages 6–12; Luscombe–Owens uses 3 × completed age + 7 for ages 1–13. The calculator does not measure or validate an individual child’s weight.
The revised APLS 6–12 branch and Luscombe–Owens use the same 3 × age + 7 arithmetic in this range. The page therefore shows one Luscombe–Owens result and identifies the shared APLS arithmetic instead of duplicating the same number. At age 13, only Luscombe–Owens remains within its cited page range.
Current guidance generally favors measured or reliable recent or caregiver-reported weight. When those are unavailable, an appropriate length-based method, ideally accounting for body habitus, is often more accurate than a simple age formula. Historical age-only formulas remain legacy or reference estimates where a local workflow names them; this is not a universal four-step hierarchy.
Systematic reviews find low overall accuracy and potentially substantial individual error. Age alone does not capture height, body habitus, illness, population, country, or era differences. Age formulas may underestimate where obesity is more common and overestimate where malnutrition is more common; no formula verifies a child’s true weight.
No. This page uses completed age only and is not pediatric ideal or adjusted body weight, weight-for-height, BMI or BMI-for-age, weight-for-age percentile, a healthy-weight assessment, or a growth chart. Those tasks require measured anthropometrics, age- and sex-specific growth references, or another specialized method.
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.