The APLS (Advanced Paediatric Life Support) weight estimation formula is a rapid bedside tool used by emergency clinicians to estimate a child's weight in kilograms when it cannot be measured directly. In emergencies, weight is critical because virtually all drug doses, fluid boluses, and equipment sizes are weight-based in paediatrics. The primary APLS formula — Weight (kg) = 2 × (age in years + 4) — applies to children aged 1 to 10 years. For infants under 1 year, a different approximation is used: approximately 0.5 kg per month up to 6 months, then slower gain. The Best Guess formula, Weight (kg) = 3 × age + 7, tends to perform better for older children (over 5 years) and in populations where children are larger than historical UK norms. The Broselow tape is a colour-coded length-based tool providing weight estimation alongside pre-calculated drug doses and equipment sizes for each colour zone, widely regarded as the gold standard when a tape can be applied. Length-based estimation consistently outperforms age-based formulae because weight gain varies more by height than age. Despite its limitations, the APLS formula remains embedded in resuscitation training worldwide because it requires no equipment, is fast to apply, and provides a clinically safe starting point. All emergency drug doses — adrenaline, atropine, glucose, lorazepam, crystalloid boluses — are calculated from this estimated weight, making accuracy vital to patient safety.
APLS Weight (kg) = 2 × (age_years + 4) [for age 1-10yr]; Best Guess = 3 × age_years + 7; Infant (<1yr) ≈ 0.5 kg/month (up to 6mo) then ~0.25 kg/month; Broselow tape: length-based colour zone lookup
- 1Determine the child's age in whole years from history or documentation; if unknown, use the Broselow tape measured from crown to heel.
- 2For children aged 1-10 years apply the APLS formula: add 4 to the age in years, then multiply by 2 to obtain estimated weight in kilograms.
- 3For children older than 5 years, or in populations known to be larger, consider the Best Guess formula (3 × age + 7) as it tends to give higher and more accurate estimates for older children.
- 4For neonates and infants under 1 year, use birth weight plus incremental gain: approximately 0.5 kg/month for the first 6 months, slowing thereafter; a term neonate weighs approximately 3.5 kg.
- 5If a Broselow tape is available, lay it alongside the supine child from the top of the head to the heel and read the colour zone — each zone provides pre-calculated drug doses and equipment sizes without needing weight.
- 6Record the estimated weight clearly in the resuscitation documentation and use it consistently for all drug and fluid calculations throughout the resuscitation.
- 7Verify against actual weight as soon as a scale is available and recalculate doses if the discrepancy is clinically significant (>20% difference).
Adrenaline 0.1 mL/kg of 1:10,000 = 1.4 mL; fluid bolus 10 mL/kg = 140 mL NS
APLS formula gives 14 kg for a 3-year-old. Drug doses and fluid boluses are then derived directly from this weight, making a rapid and reliable estimate essential.
Best Guess typically more accurate for school-age children; use 28 kg
The 6 kg difference between the two formulae is clinically significant. For older children, the Best Guess formula has been shown to correlate more closely with actual weights in modern populations.
Resuscitation adrenaline = 0.1 mL/kg 1:10,000 = 0.54 mL
Infants gain approximately 0.5 kg per month in the first 6 months. Knowing birth weight improves accuracy significantly compared to using a generic formula.
Tape provides adrenaline, atropine, glucose, lorazepam, and equipment sizes directly
The Broselow tape removes the calculation step entirely by providing colour-coded, pre-calculated doses at the bedside, reducing cognitive load during resuscitation.
Emergency drug dose calculation for adrenaline, atropine, glucose, lorazepam, and other resuscitation drugs in paediatric cardiac arrest., representing an important application area for the Pals Weight in professional and analytical contexts where accurate pals weight calculations directly support informed decision-making, strategic planning, and performance optimization
Fluid resuscitation volume calculation — 10-20 mL/kg NS boluses in septic shock or trauma., representing an important application area for the Pals Weight in professional and analytical contexts where accurate pals weight calculations directly support informed decision-making, strategic planning, and performance optimization
Equipment size selection — endotracheal tube size (age/4 + 4), blade size, and laryngeal mask size all derive from weight or age., representing an important application area for the Pals Weight in professional and analytical contexts where accurate pals weight calculations directly support informed decision-making, strategic planning, and performance optimization
Calculating defibrillation energy — 4 J/kg for paediatric VF/pVT, updated after each shock., representing an important application area for the Pals Weight in professional and analytical contexts where accurate pals weight calculations directly support informed decision-making, strategic planning, and performance optimization
Teaching and simulation: APLS and PALS courses worldwide use weight estimation as a core curriculum component to prepare trainees for real emergencies., representing an important application area for the Pals Weight in professional and analytical contexts where accurate pals weight calculations directly support informed decision-making, strategic planning, and performance optimization
Premature Neonates
In the Pals Weight, this scenario requires additional caution when interpreting pals weight results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when pals weight calculations fall into non-standard territory.
Obese Children
In the Pals Weight, this scenario requires additional caution when interpreting pals weight results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when pals weight calculations fall into non-standard territory.
Children with Chronic Illness or Malnutrition
In the Pals Weight, this scenario requires additional caution when interpreting pals weight results. The standard formula may not fully account for all factors present in this edge case, and supplementary analysis or expert consultation may be warranted. Professional best practice involves documenting assumptions, running sensitivity analyses, and cross-referencing results with alternative methods when pals weight calculations fall into non-standard territory.
Cardiac Arrest in the Older Child
{'title': 'Cardiac Arrest in the Older Child', 'body': 'In children over 12-14 years approaching adult size, adrenaline and defibrillation energy may reach adult ceilings. Adrenaline maximum is 1 mg regardless of weight; defibrillation maximum with standard paediatric calculation (4 J/kg) should be capped at adult energies (360 J monophasic or 200 J biphasic) if estimated weight exceeds 50 kg.'}
| Age | APLS Formula (kg) | Best Guess (kg) | Typical Broselow Zone |
|---|---|---|---|
| 1 year | 10 | 10 | Pink |
| 2 years | 12 | 13 | Red |
| 3 years | 14 | 16 | Purple |
| 5 years | 18 | 22 | Yellow |
| 7 years | 22 | 28 | White |
| 10 years | 28 | 37 | Blue/Orange |
Which formula is most accurate for paediatric weight estimation?
Length-based tools like the Broselow tape consistently outperform age-based formulae. Among age-based formulae, the Best Guess formula (3 × age + 7) performs better for children over 5 years, while APLS is preferred for younger children aged 1-5 years. This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
Can the APLS formula be used for children over 10 years?
The APLS formula is validated for children aged 1-10 years. For children over 10 years, adult weight estimation or direct measurement is preferred, as the formula significantly underestimates weight in older or larger children. This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
Why does weight matter so much in paediatric emergencies?
In paediatrics, virtually all drug doses, fluid volumes, and equipment sizes are weight-based. An error in weight estimation directly translates to dosing errors, which can cause underdosing (ineffective resuscitation) or overdosing (toxicity), both of which can be fatal. This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
What is the Broselow tape and when should I use it?
The Broselow tape is a colour-coded measuring tape applied alongside a supine child. Each colour corresponds to a weight range with pre-printed drug doses and equipment sizes. It should be used whenever physically possible as it is more accurate than age-based formulae and eliminates calculation errors. This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
How do I estimate weight for an obese child?
Standard formulae underestimate weight in obese children. For drug dosing in obese children, ideal body weight (50th centile weight for height) should generally be used rather than actual weight, except for drugs where actual body weight is specified (e.g., succinylcholine). This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
What if the child's age is unknown?
If age is unknown and a Broselow tape is not available, estimate height visually and use a length-to-weight table. Dental development and bone age can also guide age estimation. The Broselow tape works from length and does not require knowledge of age. This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
Is the APLS formula the same worldwide?
Variants exist. The Advanced Trauma Life Support (ATLS) formula uses (age + 4) × 2, the same as APLS. Some regions use locally derived formulae. The Luscombe and Owens formula and Best Guess formula were developed to address the tendency of older formulae to underestimate weight in modern populations. This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
Should I round the estimated weight when calculating drug doses?
Generally yes — round to the nearest 0.5 or 1 kg for simplicity and to reduce calculation errors. Always apply a maximum dose ceiling (e.g., adrenaline max 1 mg regardless of weight) to avoid toxicity in unexpectedly large children. This is particularly important in the context of pals weight calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise pals weight computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.
Pro Tip
In a paediatric resuscitation, calculate and display the weight estimate prominently at the bedside. Pre-calculate the top five drug doses (adrenaline, atropine, glucose, lorazepam, fluid bolus) from this weight before they are needed — this reduces cognitive load and errors at the critical moment.
Did you know?
The Broselow tape was developed by Dr James Broselow in the early 1980s after he observed that resuscitation teams were struggling to calculate paediatric drug doses under stress. He noticed that weight correlates better with length than age, a simple insight that has since saved countless lives by converting a complex calculation into a colour lookup.
References
- ›Advanced Paediatric Life Support (APLS) 6th Edition — BMJ Books / Wiley
- ›Luscombe MD, Owens BD. Weight estimation in resuscitation: is the current formula still valid? Arch Dis Child 2007.
- ›Broselow J et al. A length-based method for estimating paediatric weight and medication dosing. Ann Emerg Med 1988.
- ›Resuscitation Council UK — Paediatric Advanced Life Support Guidelines 2021