Age Calculator: How to Find Your Exact Age in Years, Months and Days

To find your exact age, count the whole years from your date of birth, then the whole months since your last birthday, then the days left over. Someone born on 15 August 2001 is 25 years, 2 months and 0 days old on 15 October 2026. The only tricky cases are birthdays on the 29th, 30th or 31st of a month and on 29 February, where calculators can differ by a day depending on the rule they follow.

The free age calculator works this out from your date of birth to today, or to any "age on" date you choose, such as an exam's cut-off date. It also shows your age in total months, weeks, days and hours, and the number of days to your next birthday. Below is the exact method it uses, with the edge cases worked through.

The method, step by step

Take a date of birth of 31 March 1990 and find the age on 15 October 2026.

1. Whole years. The 2026 birthday (31 March 2026) has passed, so that is 36 years.
2. Whole months. Add months to 31 March 2026 for as long as you stay on or before 15 October. Six months takes you to "31 September", which doesn't exist, so it lands on the last day of the month, 30 September 2026. A seventh month would overshoot.
3. Days. From 30 September to 15 October 2026 is 15 days.

The answer is 36 years, 6 months and 15 days, which is what the calculator shows, along with a total of 13,347 days. The one rule to remember: when adding months lands on a date that doesn't exist, use the last day of that month.

Why two calculators can disagree by a day

Many people learnt a different method at school: write both dates as day, month and year, subtract column by column, and if the days go negative, "borrow" the number of days in the previous month.

For 15/10/2026 minus 31/03/1990, the days give 15 − 31 = −16. Borrowing September's 30 days gives 14 days, the months become 10 − 1 − 3 = 6, and the years 36. That method says 36 years, 6 months and 14 days, one day less than the calculator.

Both methods are consistent; they just treat month ends differently. The answers only differ when the birth date falls on the 29th, 30th or 31st, and the whole-years figure, which most eligibility rules use, is the same either way. If a form needs months and days, use one method throughout and say which one if asked.

Spreadsheets have their own quirk. In Excel, DATEDIF(birth, date, "Y") gives whole years reliably, but Microsoft warns that the "MD" option for leftover days may return a negative number, a zero or an inaccurate result, and doesn't recommend using it.

Month-end edge cases

The calculator always adds whole months first and clamps to the last day of the month when needed, so the days figure is never negative. These are its results for the awkward dates:

In plain words: one month after 31 January is the last day of February, and one month after 31 October is 30 November. The day after that is "1 month, 1 day".

Born on 29 February

A year is a leap year if it divides by 4, except century years, which must divide by 400. So 2000 was a leap year and 1900 was not, and 2100 won't be. People born on 29 February have a real birthday only once every four years; the leap year checker tells you which years qualify, and the leap year guide explains why.

In other years the calculator treats 28 February as the birthday, using the same month-end rule as above. For a birth date of 29 February 2004:

• on 27 February 2025: 20 years, 11 months, 29 days;
• on 28 February 2025: 21 years, 0 months, 0 days, with "Next birthday in: Today";
• on 1 March 2025: 21 years, 0 months, 1 day;
• on 29 February 2028: 24 years, 0 months, 0 days.

Some other calculators use 1 March instead. If a rule or form you are dealing with treats 1 March as the birthday in non-leap years, you reach the new age one day later than the tool shows.

Age "as on" a cut-off date

Exam notifications, admissions and job adverts usually ask for your age as on a fixed date, not today. Enter that date in the "Age on date" box. Suppose a rule requires candidates to have completed 21 years on 1 August 2026:

• born 1 August 2005: 21 years, 0 months, 0 days on 1 August 2026, so the condition is met;
• born 2 August 2005: 20 years, 11 months, 30 days, one day short (the tool also shows "Next birthday in: 1 day").

Many notifications state the limit as a range of birth dates, such as "born not earlier than … and not later than …". When they do, compare your date of birth with those dates directly; the notification's wording settles boundary cases, and a calculator can only confirm them. The exam cut-off guide covers age relaxations and common mistakes.

Total months, weeks, days and hours

For a birth date of 15 August 2001, on 15 October 2026 the calculator shows:

The date difference calculator gives the same 9,192 days between the two dates, but its months (302) and years (25.17) are approximations made by dividing days by an average month or year. Use it for gaps such as notice periods; use the age calculator when you need calendar months. To count down instead, the days until calculator shows the days left to any date.

Tips for getting it right by hand

• Add months to the birth date rather than assuming every month has 30 days. That shortcut drifts by several days over a year.
• Count leap days if you work in total days: each 29 February between the two dates adds one.
• Check the date format. Indian forms use DD/MM/YYYY, but some websites use MM/DD/YYYY, so 03/04 can mean 3 April or 4 March. The calculator's date picker avoids this.
• Know what the tool ignores. It works in whole days from midnight, so the time of birth and time zones don't enter the result.

Frequently asked questions

How do I calculate my age from my date of birth?

Count the whole years to your most recent birthday, then the whole months after it, then the remaining days. If adding a month lands on a date that doesn't exist, such as 31 September, use the last day of that month.

How old am I if I was born on 29 February?

You age normally; only the birthday date moves. The calculator counts your birthday as 28 February in non-leap years, so it shows the new age on 28 February. If a rule you follow uses 1 March, add a day.

Does the age calculator count the day of birth as day 1?

No. On the day you are born it shows 0 years, 0 months, 0 days, and the next day 1 day. This is the usual way age is counted.

Why does another website show one day more or less?

It probably uses the "borrow days from the previous month" method, which differs by a day for birth dates on the 29th to 31st. The whole years are the same.

How many days old am I?

Enter your date of birth and read the "Total days" line. Someone born on 15 August 2001 was 9,192 days old on 15 October 2026.

Can I find my age on a future date?

Yes. Put any date after your date of birth in "Age on date". If the date you enter is before your birth date, the calculator says so instead of showing a negative age.

Sources: Microsoft Support, DATEDIF function (known limitation of the "MD" argument); Gregorian calendar leap-year rule.