MultiKit

Age Calculator: Exact Age in Years, Months and Days

  • Free
  • No sign-up
  • Runs in your browser
  • Version 1.0.1
  • Last updated 2026-10-25
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Enter a date of birth to see the exact age in years, months and days, as of today or as of any date you choose. The page also gives the months, weeks and days lived, the weekday of birth and how many days remain until the next birthday.

Everything you enter is processed in your browser and is never sent to a server.

How to use

  1. Enter the date of birth. The age is worked out as of today.
  2. To find the age on another day, such as a cut-off date for a school or a race, change Age on to that date. Press Today to return to today.
  3. Read the age, the totals (months, weeks, days), the next birthday and the weekday you were born.

Examples

Born 1990-05-15, age on 2026-10-12
→ 36 years, 4 months and 27 days
The last birthday was 15 May 2026; from there it is 4 months and 27 days.
Born 2000-01-01, age on 2026-10-12
→ 26 years, 9 months and 11 days; next birthday in 81 days
9,781 days have passed since the day of birth.
Born 2000-02-29, age on 2026-02-28 and 2026-03-01
→ 25 years on 28 February, 26 years on 1 March
In a year without 29 February the birthday is counted on 1 March.

How it works

The page uses the date-fns library for the date arithmetic. It first works out the whole years: the difference of the years, less one if the birthday of that year has not yet come. The months and days are the interval from the last birthday to the date you chose. The total days are the difference in calendar days, and the next birthday is the first one that is not before the chosen date.

All dates are calendar dates without a time, built from the numbers you enter, so daylight saving time cannot shift a day. A date that does not exist, such as 30 February, is refused. The calculation and the leap-day rule are covered by tests, and the page is checked in a real browser.

Sources

Frequently asked questions

How is the age counted?
The age in years goes up on the birthday. The months and days are counted from the last birthday to the date you chose. This is the international way, which is also the legal age in Korea since the 2023 law unified it. It is not the traditional Korean count.
What about a birthday on 29 February?
In years without a 29 February the birthday is counted on 1 March, so someone born on 29 February 2000 is 25 on 28 February 2026 and 26 on 1 March 2026. Some places use 28 February instead; the law of your place decides.
Does the time of day or time zone matter?
No. It uses calendar dates only, in the dates you enter, so it does not change with the hour or the time zone.
Why are the days different from another calculator's?
Months have different lengths, so the days left over after the months depend on the method. This page counts months from the last birthday, then the days that remain, and the total days lived is exact.
Is anything sent to a server?
No. The dates stay in your browser.

Guides

Version history
  • 1.0.1 — Clarifies the search title with the tool's main task and whether it is free or runs online.
  • 1.0.0 — First release.

Last updated: