Age in Weeks Calculator
See exactly how many weeks old you (or your baby) are — handy for week-by-week milestone tracking, or just a different way to look at age.
How this is calculated
This tool counts the exact number of calendar days between your date of birth and today, then divides by seven to get whole weeks plus any leftover days — so a total of 100 days becomes "14 weeks, 2 days" rather than a decimal. It's the same leap-year-safe day count used across ZenCountdown, just framed around weeks instead of years. It also tracks the next "round number" milestone — the next multiple of 100 weeks above your current total — since week-based milestones are common shorthand for tracking a baby's age.
Frequently asked questions
Why track age in weeks instead of months?
Weeks are the standard unit for describing a baby's age during the first year or two — "a 12-week-old baby" pins down the age more precisely than "about 3 months," and pediatric growth and milestone charts are usually organized by week for that reason.
How many weeks are in a year?
52 weeks and 1 day in a common year, or 52 weeks and 2 days in a leap year. This calculator uses the exact day count between your two dates rather than a rounded 52-week estimate, so it stays accurate over many years.
Does this handle leap years correctly?
Yes. It counts real calendar days between your date of birth and today rather than approximating with 365.25 days per year, so leap years are already built into the total.