Age calculator
Enter a date of birth to see the exact age in years, months and days, the days lived and the next birthday.
Free · no signup Runs in your browser
How do I calculate my age?
Enter the date of birth. The calculator shows the age in years, months and days up to today, or up to any date you choose, plus the number of days lived and the date of the next birthday. It counts whole calendar days, so the answer is exact and is not thrown off by daylight saving time.
How an exact age is counted
An age is the number of complete years since birth, then the complete months left over, then the days left over. The part that trips people up is borrowing: if the birthday day-of-month is later than today's, a month is borrowed, and the number of days in that borrowed month is added. Counting from 31 December to 1 March gives a different number of days depending on whether February had 28 or 29, so a good calculator works with the calendar instead of dividing days by 365.
The Gregorian calendar has a leap year every four years, except century years that are not divisible by 400, so 2000 was a leap year and 1900 was not. A person born on 29 February has a birthday only in leap years; this tool treats it as 1 March in the other years, which is the convention many offices use, while some places use 28 February. You can also choose a different 'age on' date to find out how old someone will be, or was, on a particular day, for example the cut-off date for a school year or a benefit.
It runs in your browser. The dates you enter are never sent anywhere.
When to use it
- Finding exact age for a form, a school cut-off or an age-limited offer
- Counting how many days old a baby or a pet is
- Checking how old someone was on a past date
- Finding the days left until a birthday
Mistakes it helps you avoid
- Dividing the days by 365, which ignores leap years.
- Forgetting that months have different lengths when borrowing days.
- Using a date in the wrong order: the field uses year-month-day.
- Assuming everyone treats a 29 February birthday the same in a common year.
The formula
How the answer is worked out.
years = complete years from the birth date to the chosen datemonths = complete months left over after the yearsdays = days left over, borrowing the length of the month before the chosen date when neededdays lived = the number of calendar days between the two datesnext birthday = the next date with the same month and day (1 March for 29 February in a common year)
Dates are handled as calendar dates in UTC, with no time of day, so there is no daylight-saving error and the result is the same in every time zone. Leap years follow the Gregorian rule. Hours lived are days × 24, an approximation since the time of birth is not asked.
Example: born March 15, 1990
You want the exact age on October 25, 2026.
- Years36 (the 36th birthday was on March 15, 2026)
- Months7 (to October 15, 2026)
- Days10 (to 25 October)
36 years, 7 months, 10 days
Days lived: 13,373 on that date.
Terms on this page
- Leap year
- A year with an extra day, 29 February, to keep the calendar in step with the seasons.
- Gregorian calendar
- The calendar in everyday use in Canada and most of the world.
Common questions
How do I calculate age from a date of birth?
Count the complete years, then the complete months left over, then the days. The calculator does this for any date.
How is a 29 February birthday counted?
As 1 March in years that are not leap years. Some organisations use 28 February instead.
Can I find an age on a past or future date?
Yes. Enter the date in the 'Age on' box.
Is anything I enter sent to a server?
No. The calculation happens in your browser and nothing you type leaves your device.
How many days old am I?
The 'days lived' figure is the exact number of days between your birth date and the chosen date.
Where these numbers come from
- Wikipedia — Gregorian calendar The leap-year rule and month lengths used in the calculation.
- W3C — Date and Time Formats (ISO 8601 profile) The YYYY-MM-DD form used for dates.
- MDN Web Docs — Date.UTC() How a browser counts calendar days without daylight-saving shifts.
Last verified 2026-10-25 The method on this page is checked against the sources above at least once a year. Spotted something out of date? Tell us and we will fix it.
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