Age Calculator
Age Calculator by Date of Birth
Enter your date of birth below to get your exact age. Here is exactly how the calculation works, and what to do if you only know part of your birth date.
Enter your date of birth
Defaults to today — change it to find your age on any date.
How age is calculated from a date of birth
Your age is the gap between your date of birth and today. We first count the full years, then the leftover months, then the leftover days — borrowing from the previous month when needed so the day count never goes negative.
Example: born 14 March 2000, with today being 18 June 2026. That is 26 full years, then from 14 March to 18 June is 3 months and 4 days — so the exact age is 26 years, 3 months and 4 days.
What if you only know the birth year?
If you only know the year, subtract it from the current year for an approximate age. Be aware this can be off by one: someone born in 2000 is 26 in 2026 only after their birthday — before it, they are still 25.
Births on 29 February
If you were born on a leap day, your exact age still advances every year; most people mark the birthday on 28 February or 1 March in non-leap years. The day count from your DOB stays accurate either way.
The month-end cases that trip calculators up
Months are not the same length, so "one month after 31 January" has no obvious answer. A correct age calculation clamps to the last valid day of the target month rather than rolling over into the next one — otherwise ages briefly jump forward and then back again, which is why some calculators disagree by a day at month ends.
| Born | Age measured on | Result | Why |
|---|---|---|---|
| 31 January 2000 | 28 February 2026 | 26 years, 0 months, 28 days | February has no 31st, so the month is not yet complete |
| 31 January 2000 | 31 March 2026 | 26 years, 2 months, 0 days | Both months complete on the same day number |
| 29 February 2000 | 28 February 2026 | 25 years, 11 months, 30 days | 2026 is not a leap year |
| 29 February 2000 | 1 March 2026 | 26 years, 0 months, 1 day | The birthday has passed |
| 30 April 2000 | 31 May 2026 | 26 years, 1 month, 1 day | Full month plus one leftover day |
How each case is resolved.
Getting the date format right
More age errors come from format confusion than from arithmetic. 03/04/2000 is 3 April in most of the world and 4 March in the United States, and a form that reads it the other way can shift an age by months.
When you type a date manually, prefer an unambiguous form — 3 April 2000, or the ISO form 2000-04-03. Use the date picker above rather than typing when you can, so the day and month cannot be swapped.
If you only know part of the date
- Year only — subtract from the current year, and treat the result as accurate to within one year.
- Month and year — you can say the age exactly once that month has passed this year.
- An approximate age instead of a birth date — subtract the age from the current year for a birth-year estimate, but expect a one-year spread.
- Two conflicting documents — official processes almost always use the date on the birth certificate.
Age on a date other than today
Plenty of questions are not about today: how old a child will be on the first day of school, your age on a policy renewal date, or how old someone was at a past event. The same method works — replace today's date with the date in question and count years, then months, then days.
This is worth doing deliberately for admission cutoffs, where being a few days either side of a fixed date decides the school year a child enters.
Frequently asked questions
How do I calculate my age from my date of birth?
Subtract your birth year from the current year, then reduce it by one if your birthday has not happened yet this year. For the exact figure, enter your date of birth above to get years, months and days.
Is the age based on today's date?
Yes. The calculator compares your date of birth with today's date, so the result is always your age as of today.
Why do two age calculators sometimes differ by a day?
Almost always because of month-end handling — whether "one month after 31 January" clamps to 28 February or rolls into March. Clamping to the last valid day of the month is the convention used here.
Does my time zone affect the result?
Only around midnight, when your device's date may differ from the date somewhere else. The age itself is calculated from calendar dates, so it is stable for the rest of the day.
Which date format should I enter?
Use the date picker so day and month cannot be confused. When writing a date by hand, prefer 3 April 2000 or the ISO form 2000-04-03 over 03/04/2000.