How to Calculate Age in Years, Months and Days
Published 2026-11-02
Age calculator and “how old am I” are huge date searches. The answer people want is not total days divided by 365.25. It is the way birthdays work: complete years, then leftover months, then leftover days.
Use the free tool
Run these formulas with your own numbers. Math stays in your browser.
Open Age Calculator →Our age calculator uses that civil-calendar count and also shows total days lived. Dates are calendar dates, not time-zone clocks. The days-between-dates calculator is the right tool when you only want a day count between two dates.
Open the age calculator
Enter a birth date and an as-of date (today after the page loads). You will see years, months and days plus total days. Nothing is sent to a server.
How the count works
The tool walks complete years first, then complete months, then leftover days. If the as-of day-of-month is before the birthday in that month, it borrows a month. If adding a month lands on a date that does not exist (January 31 plus one month), civil calendars move to the last day of the shorter month.
Years = complete birthdays up to the as-of date
Then leftover months, then leftover days
Total days = as-of calendar date − birth calendar date
Leap-day birthdays
Someone born on 29 February does not get a civil birthday in common years. Conventions differ by country and by institution. This calculator still produces a consistent year/month/day breakdown from the two calendar dates you type — it is not a legal-age ruling for a specific jurisdiction.
| Born | As of | What you read |
|---|---|---|
| 2000-01-01 | 2026-01-01 | 26 years, 0 months, 0 days |
| 2000-01-01 | 2026-01-08 | 26 years, 0 months, 7 days |
Age vs days between
Total days lived is a single integer. “Business days between two dates” is a different question — use the days-between-dates calculator. Adding or subtracting a duration from a date is the date calculator. Hours and minutes between clocks are the hours or time calculators. “Age calculator” and “how old am I” stay near the top of date searches because forms want years-months-days, not a raw day count. Leap-day birthdays and time zones are why a phone clock and this page can disagree by a day if you type the wrong calendar date — enter the civil dates, not the local clock.
- Enter the birth date as a calendar day.
- Set the as-of date (leave it on today unless you are dating a past event).
- Read years, months and days.
- Use total days if a form asked for an age in days (some clinical contexts do).
- Do not use this tool as a legal-age certificate.
Use the free tool
Run these formulas with your own numbers. Math stays in your browser.
Open Age Calculator →Frequently Asked Questions
Does time of day matter?
No. These are calendar dates, not timestamps.
Why isn’t age just days ÷ 365?
Years have 365 or 366 days, and months have 28–31 days. Birthday counting follows the calendar, not a fixed 365.
Can the as-of date be before the birth date?
That is not an age. Use dates in order, or use days-between-dates if you want a signed span.
Is this my legal age?
Legal age can depend on local midnight and leap-day statutes. This is a calendar estimate.
Will my timezone change the day?
The tool uses the calendar dates you enter, not your clock.