Methodology

Every calculator on this site is built from the original published reference. This page documents the methodology, sources, and assumptions behind each tool.

Last reviewed: June 25, 2026

ASQ-3 scoring

Scores are computed per domain using the standard 0/5/10 weighting and compared to the age-interval cut-offs published in the ASQ-3 User's Guide (Squires & Bricker, Brookes Publishing). Where the form indicates an item should be averaged for missing responses, we apply the same convention.

Growth percentiles

We use the WHO Child Growth Standards (0–24 months) and the CDC growth charts (2–20 years). Z-scores are computed using the LMS method published with each reference. For preterm infants under 24 months we use corrected age.

Corrected age

Corrected age = chronological age − (40 weeks − gestational age at birth). We apply correction up to 24 months for developmental screening and up to 36 months for growth, consistent with AAP guidance.

Sleep recommendations

Daily sleep totals follow the AASM consensus recommendations endorsed by the AAP. Bedtime calculations work backwards from desired wake time using age-appropriate sleep totals and typical sleep-cycle length.

BMI

Child BMI is calculated as weight (kg) ÷ height² (m²) and categorised using CDC age- and sex-specific percentiles.

Assumptions and limits

  • Inputs are validated for plausible physiologic ranges; out-of-range values are flagged rather than scored silently.
  • Results are rounded for display but computed at full precision internally.
  • None of these tools replace a clinical evaluation.

Full citations are listed on the Sources page.