Age Calculator
This free age calculator turns a date of birth into an exact age in years, months and days — with proper calendar borrowing, not a rough estimate.
How to use
- Pick the date of birth; the age in years, months and days appears immediately.
- Optionally set an as-of date to compute the age at another moment — leave it empty for today.
- Read the exact age and the count of days until the next birthday (shown as "today" on the day itself).
- Adjust either date freely to check ages at anniversaries, deadlines or historical dates.
Frequently asked questions
How is age in years, months and days calculated?
It is computed by calendar borrowing, the way you would count by hand: subtract years, then months, then days; when the day count goes negative it borrows the length of the previous calendar month (28–31 days), and when months go negative it borrows 12 months. Leap years are fully respected.
What happens for people born on February 29?
In non-leap years there is no February 29, so this tool counts March 1 as the birthday: on February 28 the age has not yet incremented, and from March 1 it has. For example, someone born 2000-02-29 turns 25 on 2025-03-01.
How many days are there until the next birthday?
The calculator shows the number of days from the as-of date to the next occurrence of the birthday, using the same February 29 convention (March 1 in non-leap years). On the birthday itself it shows "today".
Why is there an optional as-of date?
Age is normally measured against today, but many real questions are about another moment: age at signing a contract, age on an exam date, or someone’s age in an old photo. Set the as-of date to any day and both the age and the next-birthday countdown are computed against it.
Is the birth date sent to a server?
No. The whole calculation runs in your browser on your own device. Dates you enter are never uploaded, stored or logged — they vanish as soon as you close or reset the page.
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About this tool
This free age calculator turns a date of birth into an exact age in years, months and days — with proper calendar borrowing, not a rough estimate. It answers the questions that actually come up: How old exactly is someone today? How many days until their next birthday? How old was the bride on her wedding date, or the candidate on the closing date of a job posting? To make such questions answerable for any date — not just today — an optional as-of date lets you anchor the calculation to a contract date, an exam deadline or any historical moment, which is also handy for genealogy. The math follows real calendar rules: month lengths including leap years are respected, and days are borrowed the way people count them by hand. One convention is stated openly: people born on February 29 have their birthday on March 1 in non-leap years, so their age increments on March 1. Everything is computed locally in your browser the moment you pick a date — birth dates are sensitive personal data, and here they never leave your device: no upload, no storage, no logging.