Baby Age Calculator

How the Baby Age Calculator Works

Converts a baby's date of birth into their exact current age, expressed both in weeks (useful for the early months) and in calendar months (useful once weekly tracking becomes less practical). Pure date arithmetic — this tool makes no claims about what milestones should occur at what age.

Formula

Age in Weeks = floor((Today − DOB) ÷ 7 days) · Age in Months = calendar months elapsed since DOB

Weeks are counted as whole 7-day blocks since birth. Months use calendar month/day arithmetic (like a birthday counting up from the date of birth), not a flat days ÷ 30 approximation, so the count stays accurate across months of different lengths.

Calculation Example

A baby born on May 1 checked on August 13 is 14 weeks, 2 days old, or about 3 months, 1 week.

Frequently Asked Questions

Why show both weeks and months?

Pediatric appointments and early tracking are usually discussed in weeks for the first few months, then in months afterward — this tool gives both so you can use whichever your provider or record asks for.

Does this tell me about developmental milestones?

No. This tool only computes elapsed time from the date of birth — it makes no claims about what a baby should be doing at any given age. Talk to a pediatrician for developmental guidance.