Age Calculator: Exact Age in Years, Months and Days

About this age calculator

This calculator tells you how much time lies between a date of birth and another date, in the three units people actually quote: completed years, completed months and leftover days. Type a birth date in the Date of birth field and the Years, Months and Days boxes fill in at once. The second field, Calculate age on, starts as today, so the first result you see is your age right now.

The second date is where the tool becomes more than a birthday counter. Change it to a school cut-off, a form deadline, an exam date or a date in the future and you get the age on that day. Parents checking admission rules, candidates filling an exam form and people planning a milestone birthday all need exactly that: age as on a stated date, not age today.

Counting by hand is easy to get wrong because months are not the same length. A gap from 31 January to 1 March is not obviously one month, and a leap day adds another wrinkle. The calculator follows one fixed borrowing method every time, which this page explains step by step so you can check any result yourself and know what it means for edge cases.

How to use the Age Calculator, step by step

1. Enter the date of birth. Click the Date of birth field and pick the day, month and year from the date picker, or type them in the format your browser shows. The tool opens with 12 March 2000 filled in, so replace it with your own date.
2. Check the Calculate age on date. This field is set to today when the page loads. Leave it alone for your current age. For an age on a particular day, such as an admission cut-off, replace it with that date before reading the result.
3. Read Years, Months and Days. The result box shows three numbers. Years and Months are completed ones, and Days is what is left over. Together they read as one age, for example 26 years, 7 months and 8 days.
4. Keep the end date after the birth date. The end date must be the later one. If you enter it the wrong way round, the tool does not warn you, and the numbers it shows are not a real age. Swap the two dates if the answer looks odd.
5. Try several end dates. Change only the Calculate age on field to compare dates, for instance 31 March against 1 April. The result updates the moment you pick a new date, so you can test a few cut-offs in under a minute.
6. Do not clear the birth date. If the Date of birth field is emptied or incomplete, the calculator stops and leaves the previous numbers on screen. Those numbers are stale, so always enter a full valid date before trusting what you see.

The formula behind the Age Calculator

The calculator subtracts the two dates part by part, then fixes any negative number by borrowing from the next larger unit. This is the same method you were taught for subtracting numbers on paper.

Years = End year − Birth year
Months = End month − Birth month
Days = End day − Birth day
If Days < 0: Months = Months − 1, then Days = Days + (number of days in the month before the end date's month)
If Months < 0: Years = Years − 1, then Months = Months + 12

What each symbol means

End year / month / day

The year, month number (January = 1) and day of the month of the "Calculate age on" date.

Birth year / month / day

The same three parts of the date of birth.

Years

Completed years shown in the Years box after any borrowing.

Months

Completed months beyond those years, always between 0 and 11 in a normal result.

Days

Leftover days beyond the completed months.

Days in the month before the end date

The length of the calendar month that comes just before the month of the end date: 31 for March, 28 or 29 for March in some years, and so on. This is the number added when Days goes negative.

How the formula works

The logic is the paper method of subtraction. Take 10 June 2015 and 1 April 2026. Years give 11, months give 4 − 6 = −2 and days give 1 − 10 = −9. Nobody is minus nine days old, so the calculator borrows a month. That month has to be turned into days, and it uses the month just before the end date, here March 2026 with 31 days. Days becomes 22 and Months drops by one to −3.

Months is now negative, so it borrows a year in the same way: Years drops from 11 to 10 and Months gains 12, giving 9. The final answer is 10 years, 9 months and 22 days. Always borrow days first and years second. The order matters, because the day borrow can push the month count below zero, and that is what triggers the year borrow.

Borrowing from the month before the end date has a visible effect when a birth date falls on the 29th, 30th or 31st. Between 31 January and 28 February of the same year the tool shows 0 years, 0 months and 28 days, but on 1 March it shows exactly 1 month, even though only 29 or 30 days have passed. Other tools may choose to borrow from a different month, so a one-day difference between two calculators is normal, not a bug.

Counting the total days between two dates is a separate question. The calculator reports years, months and days, not a single day total. For a day count, add up the days in the months between the dates using the table below. From 1 January to 1 March 2026 that is 31 + 28 = 59 days. If you want both the first and last day counted, add one. The leap-year rule is simple: a year is a leap year if it divides by 4, except century years, which must divide by 400. So 2000 and 2024 are leap years, while 1900 and 2100 are not.

Worked examples

Exact age today, no borrowing needed

Aarav was born on 17 August 2005. He wants to know his exact age on 23 October 2026.

1. Years = 2026 − 2005 = 21.
2. Months = 10 − 8 = 2 (October is month 10, August is month 8).
3. Days = 23 − 17 = 6.
4. None of the three is negative, so there is nothing to borrow.
5. As a check, the real gap between the two dates is 7,737 days, which is about 21.18 years.

Result: 21 years, 2 months and 6 days.

Age on a 1 April admission cut-off

A school asks for the child's age as on 1 April 2026. The child was born on 10 June 2015.

1. Years = 2026 − 2015 = 11. Months = 4 − 6 = −2. Days = 1 − 10 = −9.
2. Days is negative, so Months becomes −2 − 1 = −3.
3. The month before April 2026 is March, which has 31 days, so Days = −9 + 31 = 22.
4. Months is still negative, so Years becomes 11 − 1 = 10 and Months becomes −3 + 12 = 9.
5. Check: the real gap is 3,948 days, which fits 10 years, 9 months and 22 days.

Result: 10 years, 9 months and 22 days. The child has not yet turned 11 on that date.

A leap-day birthday on 28 February and 1 March

Meera was born on 29 February 2008. In 2026, which is not a leap year, what does the calculator show on 28 February and on 1 March?

1. On 28 Feb 2026: Years = 18, Months = 2 − 2 = 0, Days = 28 − 29 = −1.
2. Days is negative: Months = −1 and the month before February is January 2026 with 31 days, so Days = −1 + 31 = 30.
3. Months is negative: Years = 17 and Months = −1 + 12 = 11. So 28 Feb 2026 shows 17 years, 11 months, 30 days.
4. On 1 Mar 2026: Years = 18, Months = 3 − 2 = 1, Days = 1 − 29 = −28. Days is negative, so Months = 0 and the month before March is February 2026 with 28 days, so Days = −28 + 28 = 0.
5. So 1 March 2026 shows 18 years, 0 months, 0 days. In a non-leap year the tool treats 1 March as the birthday.

Result: 17 years, 11 months, 30 days on 28 Feb 2026; exactly 18 years on 1 Mar 2026.

Reference tables

Days in each month and the leap-year effect

Use this table to count days between two dates by hand. The last column is the day of the year on which each month begins in an ordinary year, so subtracting two of those numbers gives the days between the first of each month.

What the calculator shows for a 29 February birthday

Born on 29 February 2008. These results come straight from the borrowing method described above, run on the end dates listed. Note the gap between 28 Feb and 1 Mar in the non-leap year 2026.

Common mistakes and tips

Always enter the later date second

If the Calculate age on date is earlier than the date of birth, the calculator does not show an error. For example, a birth date of 15 May 1990 and an end date of 14 May 1990 shows 0 years, 11 months and 29 days. That is not an age. Swap the dates and read again.

Age as on a date is not age today

Forms often ask for age as on a fixed date, such as 1 April or 31 July of the exam year. Set the Calculate age on field to that exact date rather than today. A child who is 10 years and 9 months old on the cut-off may be a full year older by the time the form is processed.

Do not subtract years alone

Taking 2026 minus the birth year overstates age for anyone whose birthday has not yet come this year. A person born on 3 July 1971 is 59 years, 11 months and 29 days old on 2 July 2031, and exactly 60 years on 3 July 2031. One day makes a full year of difference.

Know the month-end quirk

Birth dates on the 29th, 30th and 31st can give surprising month counts. For a birth date of 31 January 2026, the date 28 February 2026 shows 0 months and 28 days, but 1 March 2026 shows 1 month and 0 days. This follows from borrowing from the month before the end date.

Count days separately from age

Years, months and days is not the same as a day total. If a rule says "at least 5,000 days" or "within 90 days", count days directly with the month table or a date-difference tool. Remember that counting inclusively, with both end days counted, adds one day to the plain subtraction.

Check the official notification

Eligibility rules for admission, exams, licences and pensions differ by state, board, institution and year, and they change. Use this calculator to get the arithmetic right, but take the cut-off date, the rounding rule and any age relaxation from the official notice itself.

Where people use this calculator

School admission cut-off dates

Many schools and boards ask for a child's age as on a fixed date. A child born on 5 December 2010 is 15 years, 6 months and 26 days old on 1 July 2026. Parents can test several dates quickly. The accepted cut-off date and minimum age vary by board and state, so check the school notice.

Exam forms and eligibility

Entrance exams and recruitment forms usually state a minimum or maximum age as on a particular date. Enter your birth date, set that date in the second field, and compare the result with the limit. Relaxations for some categories exist in many notifications, and only the official notice can confirm them.

Retirement and milestone planning

People planning ahead often need the date on which they reach a particular age. Someone born on 3 July 1971 completes 60 years on 3 July 2031. Rules for retirement and pension age differ by employer and scheme, so this is the arithmetic only, not a statement of when you may retire.

Counting time between two events

The second date does not have to be today or a birthday. Use it to find how long ago something happened, such as a joining date, a policy start or the length of a course. Put the earlier event in the first field and the later one in the second, then read years, months and days.

Birthdays and milestones

Parents tracking a baby's growth in months, or anyone counting down to a big birthday, can set a future date in the second field and see the exact age on that day. It also settles friendly arguments about who is older and by how much.

Frequently asked questions

Related calculators

Results are estimates for general information. See our disclaimer and about page for how we build and check these tools.

Last reviewed: October 2026. Spotted a mistake? Tell us on the contact page.