How old are you – exactly? Knowing your exact age in years, months and days matters for job applications, government exam eligibility, school admissions, insurance and pensions. This guide explains how to calculate age from date of birth by hand, with worked examples, the tricky rules for month-ends and leap-year birthdays, how to calculate age in Excel, and how to find your age on a specific cut-off date.
How to Calculate Age from Date of Birth
The age calculation formula is simple in principle: subtract your date of birth from today's date. In practice you do it in three steps – years, then months, then days – borrowing from the next column when a number is negative, just like subtraction at school.
- Subtract the birth year from the current year.
- Subtract the birth month from the current month. If the result is negative, take away one year and add 12 months.
- Subtract the birth day from the current day. If the result is negative, take away one month and add the number of days in the previous month.
Worked Example: Exact Age in Years, Months and Days
Let us find the exact age of someone born on 23 March 1998 on 30 September 2026.
- Years: 2026 − 1998 = 28
- Months: September (9) − March (3) = 6
- Days: 30 − 23 = 7
So the person is 28 years, 6 months and 7 days old. No borrowing was needed here because both the month and the day of today are later than the birth month and day.
Example with borrowing
Now take a date of birth of 2 August 2000 and a cut-off date of 1 August 2026 – a common situation for exam age limits:
- Days: 1 − 2 is negative, so borrow a month: July has 31 days, giving 32 − 2 = 30 days, and the month becomes 7.
- Months: 7 − 8 is negative, so borrow a year: 19 − 8 = 11 months, and the year becomes 2025.
- Years: 2025 − 2000 = 25 years.
The candidate is 25 years, 11 months and 30 days old on 1 August 2026 – one day short of 26. That single day can decide eligibility, which is why an accurate age calculator matters.
Age in Days, Weeks, Months and Hours
You can also express age as a total. For the person born on 23 March 1998, on 30 September 2026 that is:
| Unit | Age |
|---|---|
| Years, months, days | 28 years, 6 months, 7 days |
| Total months | 342 months and 7 days |
| Total weeks | 1,488 weeks and 2 days |
| Age in days | 10,418 days |
| Hours | 2,50,032 hours |
To count age in days by hand, count the days in each full year (365, or 366 in a leap year) and add the days in the partial years at each end. It is much quicker with the days calculator.
Days Until Your Next Birthday
The same person's next birthday is on 23 March 2027 – 174 days after 30 September 2026, and it falls on a Tuesday. They were born on a Monday. Our age calculator shows this next birthday countdown automatically, and the date calculator tells you the day of the week you were born on for any date.
Leap Year Birthdays (29 February)
People born on 29 February only have a true birthday once every four years. For legal purposes in India, the UK and most countries, a leap year birthday is treated as reached on 1 March in common years. For example, someone born on 29 February 2008 is still 17 on 28 February 2026 and turns 18 on 1 March 2026. Many people celebrate on 28 February instead, but for official age limits the 1 March rule is the safe one to follow.
Month-End Birthdays
Birthdays on the 29th, 30th or 31st cause confusion in short months. The standard rule is to count whole months first and then the remaining days. So from 31 January to 1 March is 1 month and 1 day, not "1 month and −2 days" as some simple formulas produce. A good date of birth calculator handles this automatically.
Age on a Specific Date: Exam and Job Cut-Offs
Government exams and recruitments state an age limit "as on" a particular date. The UPSC Civil Services Examination, for example, counts age as on 1 August of the exam year, while many state and central recruitment notices use 1 January or the closing date of the application. To check eligibility:
- Find the cut-off date in the official notification.
- Enter your date of birth and the cut-off date in the age calculator (use the "age on date" box).
- Compare the result with the minimum and maximum age, adding any age relaxation for your category – typically 3 years for OBC, 5 years for SC/ST and more for persons with disabilities and ex-servicemen, as stated in each notice.
Always go by the date of birth recorded in your Class 10 certificate, which is the proof most recruiters accept.
Age for School Admission
Under the National Education Policy, many states now require a child to be 6 years old for Class 1 admission, counted as on a cut-off date such as 31 March or 1 June set by the state or school board. Nursery and kindergarten have their own minimum ages. Enter the child's date of birth and the cut-off date in the age calculator to see whether they qualify for the coming academic year.
How to Calculate Age in Excel
To calculate age in Excel or Google Sheets, put the date of birth in A2 and use the DATEDIF function:
- Years:
=DATEDIF(A2,TODAY(),"Y") - Remaining months:
=DATEDIF(A2,TODAY(),"YM") - Remaining days:
=DATEDIF(A2,TODAY(),"MD") - Total days:
=TODAY()-A2
Combine them with =DATEDIF(A2,TODAY(),"Y")&" years "&DATEDIF(A2,TODAY(),"YM")&" months". Microsoft warns that the "MD" option can give wrong results near month-ends, so double-check those cases with an online age calculator.
How to Calculate a Baby's Age in Weeks and Months
For babies, doctors and parents usually count age in weeks for the first few months and then in months up to about two years, because growth and vaccination schedules change quickly. To find a baby's age in weeks, count the days since birth and divide by 7. A baby born on 1 August 2026 is 60 days old on 30 September 2026 – that is 8 weeks and 4 days, or 1 month and 29 days. Vaccination schedules in India (such as the 6-, 10- and 14-week doses) are counted this way. For premature babies, paediatricians often use a "corrected age", counted from the original due date rather than the actual birth date, when checking development milestones.
Age Milestones in India
| Age | Milestone |
|---|---|
| 6 years | Class 1 admission in most states |
| 16 years | Learner licence for gearless two-wheelers up to 50cc |
| 18 years | Voting, driving licence for cars and motorcycles, legal adulthood |
| 21 years | Minimum legal marriage age for men; minimum age for many government jobs |
| 25 years | Minimum age to contest Lok Sabha and Vidhan Sabha elections |
| 60 years | Senior citizen for income tax and many schemes; retirement age for most central government employees |
Government employees can find their exact retirement date with our retirement date calculator.
Common Mistakes When Calculating Age
- Subtracting years only. 2026 − 1998 = 28, but if the birthday has not come yet this year, the person is still 27.
- Using 30 days for every month. Months have 28 to 31 days; always borrow the actual length of the previous month.
- Dividing total days by 365. This ignores leap years and drifts by about a day every four years.
- Using the wrong cut-off date for an exam – always read the notification.
- Mixing date formats. 03/04/1998 is 3 April in India but 4 March in the United States.
Frequently Asked Questions
How do I calculate my exact age from my date of birth?
Subtract your birth year, month and day from today's year, month and day, borrowing a year (12 months) or a month (the days in the previous month) when a result is negative. Or enter your date of birth in the age calculator for an instant answer.
How old will I be on a particular date?
Use the same method with the future date instead of today, or enter the date in the "age on date" box of the age calculator. This is how exam and job age limits are checked.
How is age calculated for someone born on 29 February?
For legal purposes the birthday is usually treated as 1 March in common years, so the person becomes a year older on 1 March.
How do I calculate age in Excel?
Use =DATEDIF(A2,TODAY(),"Y") for completed years, "YM" for remaining months and "MD" for remaining days, where A2 holds the date of birth.
How many days old am I?
Subtract your date of birth from today's date, counting 366 days for each leap year. Someone born on 23 March 1998 is 10,418 days old on 30 September 2026.
Which date of birth is used for government jobs?
The date of birth recorded in the Class 10 or matriculation certificate is generally accepted as proof of age for government recruitment.
Note: Age limits, cut-off dates and relaxations differ between recruitments, boards and states. Always follow the official notification. This article is general information.