Developmental Screening Tools
Ages & Stages Calculator
A free ages and stages calculator for pediatric providers, early interventionists, and childcare programs using the ASQ-3 or ASQ:SE-2. Enter the birth date and screening date to get exact age in months and days — the number that decides which questionnaire interval to administer.
Each ASQ questionnaire has a strict age administration window. This calculator gives you the exact age, and an adjusted-age mode for babies born three or more weeks early.
Open the Free Ages & Stages Calculator
Enter the child's birth date and the questionnaire date. You get exact age in years, months, and days, plus total months for ASQ interval selection.
Calculate Age Now →Where Exact Age Is Required
The ASQ system selects questionnaires by the child's age in months. Exact age — and adjusted age for preemies — determines which interval is valid.
Ages & Stages Questionnaires, Third Edition
Age range: 1 – 66 months
Each questionnaire interval has a strict age administration window
Ages & Stages Questionnaires: Social-Emotional, Second Edition
Age range: 1 – 72 months
Interval selected by age in months, adjusted for prematurity
Corrected age for children born ≥3 weeks early
Age range: Until 24 months
Subtract weeks premature before selecting the interval
Early intervention eligibility and service plans
Age range: 0 – 36 months
Age reported in total months on referral and IFSP forms
Pediatric developmental surveillance
Age range: 0 – 5 years
ASQ commonly administered at 9, 18, and 30 months
ASQ used to meet the 45-day screening requirement
Age range: 0 – 5 years
Exact age on the screening date selects the interval
Adjusted Age: The Step Most Often Missed
ASQ guidance is to use adjusted (corrected) age for children born three or more weeks premature, up until 24 months. Skip the adjustment and you may administer a questionnaire interval that is too old for the child — making delays appear where there are none.
Example — ASQ-3 for a preemie
Chronological age
10 months, 6 days
Born premature
6 weeks early
Adjusted age for ASQ interval selection
8 months, 22 days → select the interval whose window contains 8m 22d
Always match the adjusted age against the questionnaire's printed age window. Full prematurity adjustment guide →
How to Use This Ages & Stages Calculator
Enter the child's birth date
Select the birth month, day, and year.
Set the screening date
Enter the date the questionnaire is completed. For mailed or take-home questionnaires, use the date the caregiver fills it out.
Adjust for prematurity if needed
If the child was born 3+ weeks early and is under 24 months, subtract the weeks premature to get adjusted age before choosing the interval.
Select the questionnaire interval
Match the age in months against the ASQ questionnaire age windows and administer the interval whose window contains the child's age.
Frequently Asked Questions
What is an ages and stages calculator?
A tool that works out a child's exact age in months and days so you can select the correct ASQ questionnaire interval. Each ASQ-3 interval has a defined age administration window — using the wrong one invalidates the screening.
Why does exact age matter for ASQ-3 screening?
If the child's age falls outside the administration window of the questionnaire you used, the cutoff scores no longer apply and the result is not valid. Age in months and days ensures the right interval.
Do I use adjusted age for premature babies on the ASQ?
Yes — for children born 3 or more weeks early, use adjusted age until 24 months. Subtract the weeks premature from chronological age, then select the interval.
How do I calculate age for the ASQ:SE-2?
The same way as ASQ-3: exact age in months from birth date to completion date, adjusted for prematurity until 24 months, then choose the interval whose window contains that age.
Is this ages and stages calculator free?
Yes — no login or download. It returns years, months, and days, converts to total months, and includes an adjusted-age mode for preemies.
Related Guides
Prematurity and Corrected Age
How to adjust chronological age for babies born early — the ASQ rule explained.
Age in Months Calculator
Convert exact age to total months for EI and IFSP paperwork.
Brigance Age Calculator
Exact age for the Early Childhood Screens III and IED-III.
Child Age Calculator
Why exact age matters in child assessment, education, and pediatric use.