📅

Age in Days, Weeks and Months Calculator

Turn a birth date into an exact age in days, weeks, months and years — every unit at once, as of any date.

Birth date

As of date

Loading calculator…

How it works

total days = as-of − birth date · weeks = days ÷ 7 · months and years by calendar walking

The day count is exact: it subtracts the two calendar dates using a serial day number, so leap days are already inside the total. Weeks are simply that count divided by seven, while the months-and-years figure walks the real calendar — ticking a month only when the same day-of-month is reached — so it never drifts the way a flat 30-day month would. Reading age in several units at once is handy for baby milestones, visa day-counts and "how many days have I been alive" questions.

Worked example

Born 20 May 1990, as of 15 Sep 2026: that is 13,267 days, which is 1,895.3 weeks, and by the calendar 36 years, 3 months and 26 days — about 435 whole months of life.

Frequently asked questions

Why is the months figure not just days ÷ 30?

Calendar months run 28 to 31 days, so dividing by 30 drifts over time. This walks the actual months and only counts one when the same day-of-month is reached, matching how age is normally stated.

Can I find my age on a past or future date?

Yes — change the as-of date to any date on or after the birth date. Leave it on today for your current age. An as-of date before the birth date is rejected.

Are the hours exact?

The hours row multiplies whole days by 24, so it is exact to the day but does not include the time of day you were born, which the date-only inputs do not capture.

Related calculators

Age Calculator

Work out an exact age in years, months and days on any date — plus decimal age, total months, weeks, days and hours lived, the countdown to the next birthday, the weekday you were born and upcoming day-count milestones.

Date Difference Calculator

Count the exact days between two dates — optionally including the end date — and see the gap in years, months and days, weeks, hours and minutes, plus working days with weekends and US, Mexican or Spanish holidays left out.

Months Between Dates Calculator

Count the full calendar months and leftover days between two dates, the months as a decimal, years-months-days, total days and weeks — with an option to include the end date, a month-end rule matching Excel’s DATEDIF, and a month-by-month table.

Days Since a Date Calculator

Count how many days have passed since any date, up to today or a later date: days, weeks, months, years, hours and minutes, weekdays and weekend days, leap days crossed, the next anniversary and a table of day-count milestones such as 1,000 and 10,000 days.

Half Birthday and Milestone Date Calculator

Find your half birthday and big day-count milestones like your 10,000th day — with the exact weekday.

This calculator is for educational purposes. Double-check important results before acting on them.