Baby Age Calculator
Calculate your baby's exact age in weeks, months, and years. See developmental stage and days until next birthday.
Part of our Health Calculators collection.
Baby Age Calculator
Free online calculator
Results update automatically as you type
How to Use This Calculator
- 1
Enter your baby's birth date.
- 2
See exact age in weeks, months, development stage, and next birthday.
How Baby Age is Calculated
Age in days = Today − Birth Date Age in weeks = Days / 7 Age in months = Days / 30.44 Development stages: Newborn: 0–4 weeks | Infant: 1–12 months | Toddler: 1–3 years
Example Calculation
Example: Born 6 months ago
Inputs
birthDate: 2024-11-17
Result
6 months, 0 days — Older Infant
~26 weeks, 182 days. Approaching 6-month milestones.
Frequently Asked Questions
Why do doctors use weeks for newborns?
Weekly tracking captures rapid development in the first months. A 4-week-old and an 8-week-old are at very different developmental stages. Pediatricians typically switch to months at around 3 months.
What are key developmental milestones?
2 months: social smiles. 4 months: holds head up, rolls. 6 months: sits with support. 9 months: crawls. 12 months: first steps. All children develop at different rates — consult your pediatrician.