ASQ Age Calculator
Find the correct ASQ-3 questionnaire interval for a child — enter the date of birth (and the due date if the baby arrived early), and the calculator works out the chronological age, the adjusted age for premature babies, and exactly which of the 21 questionnaires to use, with every step shown.
🧮 Find the Questionnaire
📖 What Is the ASQ?
The Ages & Stages Questionnaires, Third Edition (ASQ-3) is a parent-completed developmental screening tool for children from 1 month to 5½ years of age. Parents answer about 30 simple questions covering five areas — communication, gross motor, fine motor, problem solving, and personal-social — and a professional scores the result against cutoff points for the child's age. It typically takes a parent 10–15 minutes; scoring takes a professional about 2–3 minutes.
A screening is not a diagnosis. A below-cutoff score simply flags that a child may benefit from a closer look — early support services can make a large difference, which is why screening at the right age matters.
🎯 Why the Right Interval Matters
ASQ-3 comes as 21 separate questionnaires — labelled 2, 4, 6, 8, 9, 10, 12, 14, 16, 18, 20, 22, 24, 27, 30, 33, 36, 42, 48, 54 and 60 months. Each questionnaire's questions are calibrated to what children can typically do at that age, and each has its own cutoff scores. Giving a 14-month questionnaire to a 20-month-old (or vice versa) makes the scores meaningless, because the child is compared against the wrong expectations.
Each questionnaire is valid only inside its official administration window — for example, the 20-month questionnaire covers ages 19 months 0 days through 20 months 30 days. The expanded windows leave no gaps: every age from 1 month through 66 months falls inside exactly one questionnaire.
📐 Chronological Age vs Adjusted Age
Chronological age is the child's actual age — time since birth. Adjusted age corrects for prematurity: subtract the number of weeks the baby arrived early from the chronological age. A baby born 8 weeks early has had 8 fewer weeks to develop, so judging them against full-term expectations would be unfair.
Official ASQ-3 guidance: adjust the age when a child was born 3 or more weeks before the due date and is chronologically under 2 years old. From age 2 onward, use chronological age — most children have caught up by then, and the windows widen.
✏️ Worked Example: A Baby Born 8 Weeks Early
Meera was born on 1 January 2025, but her due date was 26 February 2025 — 56 days, or 8 weeks, early. Her parents want to screen her on 16 October 2026.
- Chronological age: 16 October 2026 − 1 January 2025 = 653 days = 1 year, 9 months, 15 days (about 21.5 months).
- Prematurity check: 8 weeks early ≥ 3 weeks, and 21.5 months < 24 months → adjustment applies.
- Adjusted age: 653 − 56 = 597 days = 1 year, 7 months, 20 days (about 19.9 months).
- Interval lookup: 19.6 months falls in 19 months 0 days through 20 months 30 days → the 20-month questionnaire.
Without the adjustment, Meera would have been given the 22-month questionnaire — judged against expectations nearly two months ahead of her developmental age. That is exactly the mistake adjusted age prevents.
🏥 What Happens at a Screening?
In general terms: the parent or caregiver completes the questionnaire for the child's age interval, usually at home or in the waiting room, trying small activities with the child where needed. A professional then scores the five areas and compares each against that questionnaire's cutoff points. The result is one of three outcomes per area — on track, monitor and rescreen, or refer for a fuller evaluation. The whole process is deliberately low-pressure: it is a checkpoint, not a test the child can fail.
This page cannot reproduce any questionnaire items or scoring — those are proprietary materials. Your pediatrician, early-intervention program, or childcare provider supplies the official forms.
🗓️ ASQ-3 Administration Windows (Reference)
The official windows from the ASQ-3 age administration chart. Ages are inclusive of the start day; each window runs up to the next window's start.
| Questionnaire | Valid age window |
|---|---|
| 2 month | 1 month 0 days through 2 months 30 days |
| 4 month | 3 months 0 days through 4 months 30 days |
| 6 month | 5 months 0 days through 6 months 30 days |
| 8 month | 7 months 0 days through 8 months 30 days |
| 10 month* | 9 months 0 days through 10 months 30 days |
| 12 month | 11 months 0 days through 12 months 30 days |
| 14 month | 13 months 0 days through 14 months 30 days |
| 16 month | 15 months 0 days through 16 months 30 days |
| 18 month | 17 months 0 days through 18 months 30 days |
| 20 month | 19 months 0 days through 20 months 30 days |
| 22 month | 21 months 0 days through 22 months 30 days |
| 24 month | 23 months 0 days through 25 months 15 days |
| 27 month | 25 months 16 days through 28 months 15 days |
| 30 month | 28 months 16 days through 31 months 15 days |
| 33 month | 31 months 16 days through 34 months 15 days |
| 36 month | 34 months 16 days through 38 months 30 days |
| 42 month | 39 months 0 days through 44 months 30 days |
| 48 month | 45 months 0 days through 50 months 30 days |
| 54 month | 51 months 0 days through 56 months 30 days |
| 60 month | 57 months 0 days through 66 months 0 days |
* The official chart lists "9 or 10 month" for ages 9 months 0 days through 9 months 30 days; the 10-month questionnaire is the standard choice as it is the more stringent. Windows source: the official ASQ-3 / ASQ:SE-2 age administration chart (agesandstages.com).
⚠️ Common Mistakes
- Forgetting adjusted age for preemies. A baby born 2 months early and screened at 12 months chronological age should usually take the 10-month questionnaire, not the 12-month one.
- Adjusting past age 2. The correction stops at the second birthday; continuing it understates the child's development.
- Rounding the age. "About 20 months" can fall in the 18-month or 22-month window — the exact day matters near boundaries, which is why this calculator uses full dates.
- Using any questionnaire as a diagnosis. Screening flags areas to watch; only a qualified professional's full evaluation can identify a delay.
- Assuming this page is the screening. It only identifies the interval. The real questionnaire comes from official ASQ-3 materials.
❓ Frequently Asked Questions
The ASQ (Ages & Stages Questionnaires, Third Edition) is a parent-completed developmental screening for children aged 1 month to 5½ years. It covers five areas — communication, gross motor, fine motor, problem solving, and personal-social — using 21 age-specific questionnaires. Pediatricians, early-intervention programs, and childcare providers use it worldwide; it is published by Brookes Publishing.
Match the child's age (or adjusted age for preemies under 2) to the official administration windows. For example, 19 months 0 days through 20 months 30 days means the 20-month questionnaire. Enter the date of birth above and this calculator does the matching, including the prematurity adjustment.
Adjusted age = chronological age minus the weeks the baby was born early. A baby born 8 weeks early who is 12 months old chronologically has an adjusted age of about 10 months, and should be screened with the questionnaire for a 10-month-old. It corrects for the development time the baby missed.
Per official ASQ-3 guidance, adjust when the child was born 3 or more weeks before the due date and is chronologically under 2 years old. From the second birthday onward, use chronological age — most children have caught up by then.
It can't — the expanded ASQ-3 windows are continuous with no gaps, so every age from 1 month through 66 months sits inside exactly one questionnaire. A child exactly on a boundary (e.g. 21 months 0 days) moves up to the next interval's questionnaire.
No. This is an independent age-to-interval lookup using the published administration windows. ASQ® is proprietary to Brookes Publishing. The actual screening must use official ASQ-3 materials obtained through a qualified provider such as your pediatrician.
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