Calculate Your Exact Age

An age calculator works out how much time has passed between a date of birth and another date — normally today. Instead of counting on your fingers from one birthday to the next, it reads the real calendar: it knows that April has 30 days, that February sometimes has 29, and exactly which birthdays have already passed this year.

The result is written the way people usually say their age: complete years first, then the complete months that have passed since your last birthday, then the leftover days.

There are three common ways to express the same span of time, and they answer different questions.

• Calendar age — complete years, months and days. This is what you say out loud: “31 years, 2 months and 5 days”. Months here are real calendar months, so their length varies.
• Total number of days — one continuous count of every day you have lived, including every leap day. Useful for exact comparisons, but no longer split into years and months.
• Approximate age — dividing days by 365 or 365.25. Fast, but it drifts by a day or more, which is why AgeWise never uses it when an exact count is possible.

1. Write down the date of birth and today's date as day, month and year.
2. Subtract the birth year from the current year.
3. If today's month and day come before the birth month and day, subtract one year — that birthday has not happened yet this year.
4. Count the complete months from your last birthday up to today.
5. Count the leftover days. If today's day number is smaller than your birth day number, borrow the number of days in the previous calendar month — not a flat 30.

Example: born 15 January 2000, today 14 January 2026. The 2026 birthday has not arrived, so the answer is 25 years, 11 months and 30 days — not 26 years.

A year is not exactly 365 days long; it takes the Earth about 365.2422 days to orbit the Sun. To absorb the difference we add 29 February every four years — but skip that extra day in years divisible by 100, unless they are also divisible by 400. So 2000 was a leap year, 1900 was not, and 2100 will not be.

For an age calculator this matters in two ways. Total-day counts must include every leap day that fell in the span, and anyone born on 29 February needs a defined birthday for common years. AgeWise uses 28 February in common years so there is exactly one birthday each year.

The same method works for any two dates, not just a birthday and today. Start from the earlier date, count the complete years, then the complete months, then the remaining days. For example, from 10 March 2015 to 25 August 2026 is 11 years, 5 months and 15 days. The Date Difference calculator also shows the total number of days and weeks between the two dates.

To find how old someone will be on a future date, treat that future date as “today” and apply the same steps. Someone born on 3 June 2010 will be 18 years, 0 months and 0 days old on 3 June 2028, but still 17 on 2 June 2028. The Age on Date calculator handles past and future dates in the same way.

• Age Calculator — when you want someone’s age today, with a next-birthday countdown.
• Date Difference — when neither date is a birthday: a contract term, a project, a notice period, or the age gap between two people.
• Age on Date — when you need an age on one specific day, such as an eligibility cut-off, an exam date, or a historical event.
• Birthday Countdown — when you just want a live timer to your next birthday and its weekday.
• Age in Days — when you want one running day count and your next 1,000-day milestone.
• Days Until a Date — when you are counting down to a holiday, exam or deadline.

• Age in years, months and days. Born 12 May 1990, checked on 20 July 2026. The May 2026 birthday has passed, giving 36 years. From 12 May to 12 July is 2 complete months, and 12 to 20 July adds 8 days: 36 years, 2 months and 8 days.
• Difference between two dates. A notice period runs from 15 January 2026 to 15 April 2026. In calendar terms that is exactly 3 months, but it covers 90 days (16 + 28 + 31 + 15) — useful when a rule is written in days rather than months.
• Age on a future date. Born 3 June 2010, checked for 1 January 2030. The 2029 birthday makes 19 years; 3 June to 3 December is 6 months; 3 December to 1 January is 29 days: 19 years, 6 months and 29 days.
• A leap year in the span. 1 February to 1 March is “1 month” in any year, yet it is 29 days in 2024 and 28 days in 2025. This is why a calendar result and a day count can both be correct while looking different.
• A February 29 birthday. Born 29 February 2004, checked on 28 February 2025. 2025 has no 29 February, so AgeWise observes the birthday on 28 February and the result is exactly 21 years.

• Calendar units: complete years are counted first, then complete months, then remaining days. When a month would end past the last day of a shorter month (for example 31 January plus one month), the date is clamped to that month’s last day.
• Leap years: the Gregorian rule is used — every fourth year, except century years not divisible by 400.
• February 29: in non-leap years the birthday is treated as 28 February. Some legal systems use 1 March instead.
• Date differences: total days are an exact count of calendar days between the two dates; the end date is not counted as an extra day. Weeks, hours and minutes are converted from that day count.
• Assumptions: dates only, with no birth time or time zone; “today” is the date your device reports.

• Calendar-accurate results

  Years, months and days follow real month lengths instead of a 365-day estimate.

• Leap-day support

  Leap years are included, with February 29 birthdays handled consistently.

• No account required

  Open a calculator, enter the dates and view the result without signing up.

• Mobile-friendly

  Date fields, controls and results remain easy to use on smaller screens.

• Browser-based calculations

  The dates you enter are calculated in your browser and are not saved to an account.

More questions? Read the full FAQ or contact us.