Age Calculator
Work out an exact age in years, months and days from any birth date, and see how long a life has lasted in total months, days and weeks. The maths happens in this browser tab — nothing is sent anywhere.
Options
Age
Private by design. This page has no backend. The age is computed by JavaScript on your own device from the calendar alone — the dates you enter never leave this page.
How the three numbers are worked out
The calendar is not decimal, so an age in years, months and days cannot simply be subtracted. The calculation here works the way people do: it first takes whole years off the reference date, then whole months off what is left, and reports whatever days remain. That is the same method most official calculators use, and it is the reason the three parts always add back up exactly to the total number of days.
A quick example
For someone born on 15 May 2010 and asked on 20 February 2026, subtracting the three parts directly gives 16 years, −3 months and +5 days, which is not an age anyone can read. Borrowing a full month first gives the answer this page shows: 15 years and 9 months of complete months, then 5 further days — because from the 15th of last November to the 20th of February there really is one full month (15 Dec, 15 Jan, 15 Feb) always behind the date.
29 February birthdays
A person born on 29 February only has that calendar day in leap years. This page uses the common convention of treating the last day of February in other years — 28 February — as the birthday. So someone born on 29 February 2000 is counted as turning 1 year old on 28 February 2001, and 2 on 28 February 2002.
Dates at month-ends
Dates like 31 March to 30 April are treated as exactly one month, using the same convention: the last valid day of the target month stands in for a day that does not exist. If this page needs to borrow a day or month that falls past the end of a shorter month, it clamps the answer to the real calendar, so a result like “1 month and −1 days” never appears.
Where the day count comes from
Total days is an ordinary date difference: the heart of “every whole 24-hour day from the birth date to the reference date”. It counts 366 days across a leap year, and it does not round time of day, seconds or time zones — every date is treated as midnight in the visitor’s own time zone, which is all that is ever known here.
Common uses
Filling in age fields on forms and visa pages, checking eligibility that depends on exact age rather than the year of birth, working out anniversaries and “how many months now” questions, and planning something for a future birthday by reading the countdown under the figures.
How to use the Age Calculator
- Enter a date of birth.
- Optionally set the 'as of' date, which defaults to today.
- Read the exact age in years, months and days, plus totals and the next birthday.
Frequently asked questions
How is the age calculated?
It counts complete years, then the remaining months and days between the birth date and the target date.
Does it account for leap years?
Yes. The calculation uses real calendar months and leap years, so 29 February birthdays are handled correctly.
Can I calculate someone's age on a future date?
Yes. Set the 'as of' date to any date to see the age at that point.