Free tool
Baby Age Calculator
How old is your baby, exactly? Enter a birthday and see weeks, months and days, plus the next month mark, 100 days and the half birthday.
🔒 Everything you type stays in this browser. Nothing is uploaded or saved on our side.
How do I count my baby's age in months?
Count whole months from the birth date: a baby born on March 10 turns 1 month on April 10. This calculator does the math, including months with fewer days.
How many weeks is 3 months?
About 13 weeks. A month averages a little over 4 weeks, so 3 months lands around week 13.
Should I use adjusted age for a premature baby?
Many doctors use adjusted (corrected) age for babies born early, usually up to age 2. Ask your child's doctor which age to use for milestones.
Want more ideas? Read monthly baby photo ideas.
More free tools
Monthly photo card
Make a cute “4 months old” card for this month's photo.
Open the tool →every few monthsMilestones by age
See what the CDC lists for your child's age, with a printable checklist.
Open the tool →every dayQuestion of the day
One fun question to ask your kid tonight. Write down the answer.
Open the tool →every birthdayBirthday interview
The same 20 questions every birthday. Print it and compare years.
Open the tool →every birthdayLetter to my child
Write a letter they'll read when they're older, one prompt at a time.
Open the tool →whenever they say itKid quote card
Turn the funny thing they said into a polaroid card to share.
Open the tool →