Boring Tools

Age Calculator

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Calculate exact age in years, months, and days.

Find out exactly how old someone is — in years, months and days — as of today or as of any other date, plus the same span expressed as total days, weeks and months.

How it works

The tool counts whole calendar years, then whole months, then the leftover days between the date of birth and the “as of” date. If the day-of-month has not yet been reached, it borrows from the previous month. For example, from 15 March 2000 to 10 September 2026 is 26 years, 5 months and 26 days.

Total days is the exact number of days between the two dates. Total weeks is that divided by 7, rounded down. Total months is the years and months from the first line added together (years × 12 + months), ignoring the leftover days.

Today's date is taken from your device's clock and time zone when the page opens.

How to use it

  1. Pick or type the Date of birth.
  2. Leave As of on today's date, or change it to any other date.
  3. Read the age in years, months and days, with the totals beneath.
  4. Click Copy to copy the age as a sentence.

Options & controls

Inputs

Date of birth
A date picker. Nothing is shown until you choose a date.
As of
The date to calculate the age on. Defaults to today. Set it to a past date to see how old someone was then, or to a future date to see how old they will be.
Reset
In the title row. Clears the date of birth and sets As of back to today.

Reading the results

Results

Age (years, months, days)
The headline result, for example “26 years, 5 months, 26 days”.
Copy
Copies the age together with the total days, for example “26 years, 5 months, 26 days (9,675 total days)”.
Total days
The exact number of days between the two dates.
Total weeks
Total days ÷ 7, rounded down to a whole number.
Total months
Complete months elapsed, counting each year as 12.
Error message
“Birth date must be before the 'as of' date.” — shown when the date of birth is after the As of date. The two may be the same day (the age is then 0 years, 0 months, 0 days).

Tips & guidelines

  • To find out how long until a birthday, or an anniversary, set As of to that future date.
  • Use As of to work out an age at a particular event — school admission cut-off dates, eligibility for a benefit, or “how old was I when…”.
  • The calendar is the ordinary Gregorian one, so leap years are handled automatically.

Limits

  • Dates that fall on the 29th, 30th or 31st of a month can produce slightly unusual results when the age is counted in months and days, because months have different lengths; the Total days figure is always exact.
  • The calculation is by calendar date only. Times of day and time zones of the birthplace are not considered, and there are no other calendar systems.
  • The tool does not give a legal age for any purpose; check the rule that applies to you if it matters.

Saved in your browser

Nothing. The dates are cleared when you refresh, apart from As of, which is set to today again.

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