Chronological Age Calculator in Months

Many developmental screens and infant assessments ask for age in months only. Our free calculator gives you exact chronological age in years, months, and days. Use total days to convert to months, or read the months value directly from the result.

Click the button below to open the calculator; then enter birth date and the as-of date. The result shows years, months, days, total months, and total days so you can report age in months for ASQ, Bayley, or any form that requires it.

When Age in Months Is Required

Tools like the Ages and Stages Questionnaire (ASQ), the Bayley Scales, and many infant and toddler developmental screens use age in months to select the correct form and to interpret scores. Pediatricians, early intervention providers, and childcare programs often need a chronological age calculator in months to fill out referrals or to compare a child's development to age norms. Reporting age in years only can be too coarse for infants and young toddlers, where a few months can change which cutoff or norm band applies.

Our main calculator returns age in years, months, days, total months, and total days. Use the Total Months value when a form asks for age in months only (e.g. 14 months). The calculation follows the same standard used in assessment manuals and is free with no signup. For preemies, see our premature and adjusted age article when working with adjusted age.

Common tools that ask for age in months:

• Ages and Stages Questionnaire (ASQ)
• Bayley Scales of Infant and Toddler Development
• Infant and toddler developmental screens and referrals
• Pediatric and early intervention intake forms

Click the button below to open the calculator, enter the two dates, and use the result for ASQ, Bayley, or any tool that requires age in months.