Free Age Calculator

Calculate exact age in years, months, and days, plus total days lived and the days until your next birthday.

The age calculator works out an exact age in whole years, months, and days for any date — your own, a child's, or a historical date — using the actual calendar, so a birth on May 15 shown on August 11 reads "36 years, 2 months, 27 days" rather than an approximate decimal. It also reports the total number of days lived and the date of the next birthday with a day countdown, following the Gregorian convention that a February 29 birthday is celebrated on February 28 in non-leap years. You can compare any two dates by changing the "as of" date, and future birth dates are rejected with a clear message. Date arithmetic is calendar-exact: months and years respect their real lengths, including leap years, and no month is assumed to have a fixed number of days. Everything is computed locally in your browser — the only date involved that is not typed by you is today's date, used when the as-of field is left blank, and nothing is sent to a server.

Processed locally in your browser

How to use this calculator

How to get an exact age in under a minute

Enter the birth date, leave the as-of date blank to compare against today, and press Calculate. The result is the exact age in whole years, months, and days — not a decimal like 36.5 — because it is measured against the real calendar: a birth on May 15 shown on August 11 reads 36 years, 2 months, 27 days. Use the as-of field when you need an age on a specific past or future date, such as a contract anniversary, an eligibility cutoff, or a historical record; the calculator accepts any reference date as long as it is not before the birth date.

The three fields are the whole interaction, and every number is computed locally in your browser — dates you type are never sent to a server. If the result looks wrong, check the obvious first: the day of birth is not counted as day one, so a child born today is 0 days old, and a birthday on the 31st never creates phantom months because real month lengths are respected.

What each result means

The age itself is the count of completed calendar years, then completed months, then remaining days. Total days lived is the exact number of calendar days from birth through the day before the as-of date. Next birthday shows the date of the coming birthday with the days until it — and for February 29 births the Gregorian convention applies: the birthday is celebrated on February 28 in non-leap years, so the countdown is always meaningful.

Day of week born answers the question people most often pair with an age: what day of the week was that date? A birth on 2000-02-29 was a Tuesday, for example, and the weekday is always the weekday of the actual birth date itself — it does not shift when the leap-day celebration date clamps to February 28.

How is the result calculated?

Born May 15, 1990 — how old today?

With the birth date set to 1990-05-15 and the as-of date left blank, the calculator compares against today's date. On 2026-08-11 the result reads 36 years, 2 months, 27 days, with 13,248 days lived.

Example input and output
Input	Value
birthDate	`1990-05-15`
Result	36 years, 2 months, 27 days

A February 29 birthday

For a birth on 2000-02-29, the next birthday in 2026 falls on February 28 — the Gregorian convention — and in leap years such as 2028 it falls on February 29 itself.

Example input and output
Input	Value
birthDate	`2000-02-29`
Result	next birthday Feb 28 (non-leap years)

What is the formula and its assumptions?

Calendar-exact age decomposition

age = whole years, then whole months, then remaining days

Formula terms
Symbol	Meaning
`whole years`	complete calendar years since birth
`whole months`	complete months after the last year boundary
`remaining days`	calendar days after the last month boundary

Next birthday

next occurrence of birth month/day, with Feb 29 → Feb 28 in non-leap years

Formula terms
Symbol	Meaning
`Feb 29 → Feb 28`	Gregorian convention for leap-day births

What are the most common mistakes?

Counting the day of birth as day one — the calculator counts completed days since birth, so a child born today is 0 days old, not 1.
Treating all months as 30 days — the calculator respects real month lengths and leap years.
Assuming a February 29 birthday falls on March 1 in non-leap years — the conventional celebration date is February 28.

What are the assumptions and limitations?

The Gregorian calendar is assumed; other calendar systems (e.g. the Hijri or Hebrew calendars) are not supported.
The as-of date defaults to the visitor's local date at the moment of calculation, which can vary across time zones.
Age results are informational and should not be relied on for legal or medical determinations without verification.

Where do the numbers come from?

Encyclopaedia Britannica — Gregorian calendar

Last reviewed August 16, 2026 · Version 1.1.0 · Toolivaro does not guarantee external content.

Frequently asked questions

How is an age of "2 months, 27 days" computed?

The calculator counts whole calendar years from the birth date, then whole calendar months from that anniversary, then the remaining calendar days. Real month lengths are respected throughout, so a birthday on the 31st never creates phantom months.

When do leap-day babies celebrate in non-leap years?

Following the Gregorian convention, February 29 birthdays are celebrated on February 28 in non-leap years. The countdown uses that date, and the day-of-week and age decomposition are unaffected — the age math is anchored to the birth date itself.

Can I use a date other than today as the reference?

Yes. The as-of field lets you pick any reference date — useful for contract ages, eligibility checks, or counting to a past or future date. The birth date must not be after the as-of date, and both are validated before any result is shown.

Part of Time, date, and scheduling tools

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Reviewed by the Toolivaro editorial team per our methodology Methodology · Editorial policy