Pediatric Weight Estimate by Age Calculator (APLS)

How it works

APLS (UK 2011): 0–12 months (months + 9) ÷ 2; 1–5 years 2 × age + 8; 6–12 years 3 × age + 7. Classic: (age + 4) × 2. Best Guess: <1 y (months + 9) ÷ 2, 1–4 y 2 × (age + 5), 5–14 y 4 × age

Emergency drug doses, fluids and equipment sizes are all weight-based, but a critically ill child cannot always be weighed, so age formulas fill the gap. The original (age + 4) × 2 rule dates from the 1970s and now underestimates most children in high-income countries; the 2011 APLS update split the range into three bands, and the Luscombe and Best Guess formulas push estimates higher still to match modern growth. All are ±20% at best. Length-based tapes such as the Broselow, or parental report, beat every formula and should replace it as soon as possible. The derived figures — 10 mL/kg boluses, 10 µg/kg adrenaline, 4 J/kg shocks — are the standard paediatric life-support values and are shown so the estimate can be used immediately.

Worked example

A child of 4½ years: APLS gives 2 × 4.5 + 8 = 17 kg (classic 17 kg, Luscombe 20.5 kg, Best Guess 19 kg). Working from 17 kg: a 170 mL fluid bolus, 1.7 mL of 1:10,000 adrenaline, a 68 J shock and a 5.0 mm uncuffed tube at about 14 cm.

Frequently asked questions