Age Calculator
Enter a date of birth to get the exact age today, or on any other date. Leap-day birthdays are handled and explained.
How the age is calculated
Age is counted the way birthdays work: first the number of complete years since the date of birth, then the complete months since the last birthday, then the remaining days. The calculation uses calendar dates only, with no time of day, so time zones and daylight-saving changes cannot shift the result.
Example: someone born on 15 May 1990 is, on 26 September 2026, 36 years, 4 months and 11 days old: 36 birthdays have passed (the latest on 15 May 2026), 4 more month-days have passed (15 September), and 11 days remain to 26 September. That is 13,283 days in total. Their next birthday is on Saturday, 15 May 2027.
Birthdays on 29 February
People born on 29 February (a leap day) only have a calendar birthday every four years. In common years, this calculator counts the birthday as reached on 28 February, the last day of February. That is also how it handles month ends in general: one month after 31 January is 28 February (or 29 February in a leap year).
This is a convention, not a universal rule. Some jurisdictions treat 1 March as the date a leap-day person reaches a new age for legal purposes such as driving or voting. If a legal age matters, check the rule that applies where you live. With the 28 February convention, someone born on 29 February 2000 turned 23 on 28 February 2023.
Other ways age is counted
This calculator uses the international convention in which a baby is 0 years old at birth and gains a year on each birthday. Some East Asian traditions count differently (for example, being one year old at birth), and South Korea switched official documents to the international method in 2023. Some sources also start counting a baby’s age from the due date rather than the birth date for developmental purposes.
| Result | Meaning |
|---|---|
| Age | Complete years, then complete months, then days since the last month-day |
| Total months | Complete months lived |
| Total weeks | Total days divided by 7, with the remainder in days |
| Total days | Days from the date of birth to the chosen date (the birth day itself not counted) |
| Next birthday | The next birthday on or after the chosen date |
Common questions
Why might another calculator give a different number of days?
Different tools can differ by one day depending on whether they count the birth day itself. Here “total days” is the plain difference between the two dates, so on your first birthday you have lived 365 days (or 366 across a 29 February).
How do I find the age on a past or future date?
Change “Age on this date”. For example, to check how old someone will be on a trip date, enter that date.
Does this store the date of birth?
No. The calculation happens in your browser and nothing you enter is sent anywhere.
Sources
- ISO 8601 Date and time format, International Organization for Standardization