Age Calculator
Find your exact age in years, months, and days from your date of birth as of today or any date you choose. The calculator also shows your age as a total number of days, weeks, and months, and counts down the days to your next birthday.
Calculate
Default result: 26
Result
Years
- Months
- 3
- Days
- 23
- Total months
- 315
- Total weeks
- 1,372
- Total days
- 9,609
- Days to next birthday
- 253
How to calculate
Enter your date of birth. The 'age as of' date starts at today, but you can change it to any past or future date to see how old you were or will be then. The result updates as you type.
Years and months are counted by completed calendar periods: a year is added only once the birth month-and-day has been reached, and the same rule applies to months. The leftover days are the gap from the last completed monthly anniversary to the as-of date, measured with month-end clamping so the count is never negative. Total days = as-of date − birth date; total weeks = total days ÷ 7 (whole weeks); total months = years × 12 + months.
Example calculation
Someone born on February 29, 2000 is 26 years, 3 months, and 23 days old as of June 21, 2026 — that is 9,609 days, 1,372 whole weeks, or 315 months, with 253 days until their next birthday (observed March 1 in non-leap 2027).
- years
- 26 years
- months
- 3 months
- days
- 23 days
- totalMonths
- 315 months
- totalWeeks
- 1,372 weeks
- totalDays
- 9,609 days
- daysToNextBirthday
- 253 days
Assumptions
- Age is exact time lived, not a count of birthdays: 'years' increases only when the full birth month-and-day has been reached on or before the as-of date.
- The leftover days are measured from the most recent completed monthly anniversary of your birth date, using month-end clamping. Because months have different lengths (28–31 days), the same number of leftover days can span a different stretch of the calendar.
- A February 29 birthday is treated as March 1 for the next-birthday countdown in years that are not leap years (D-09).
- The 'age as of' date defaults to today, where 'today' is your device's local calendar date. Around midnight your local date and the UTC date can differ by a day, so an age computed just after midnight may shift by one day depending on your time zone.
- When you open a shared link the inputs come from the URL first, then from your last-used values saved in this browser, then from the calculator's defaults (which is why a shared link or a saved value can override 'today').
Common mistakes
- Assuming age advances on January 1 or counts whole birthdays only — age here is exact time lived, so it includes the partial year since your last birthday as months and days.
- Treating every month as 30 days. Months are calendar-based, so the leftover-days figure depends on which months the period crosses.
- Expecting a February 29 birthday to have no birthday in common years — the calculator counts it on March 1 so there is always a next birthday.
Frequently asked questions
Is age counted by birthdays or by exact time lived?
By exact time lived. The calculator adds a full year only once you have reached your birth month and day, then expresses the remainder as months and days. It does not simply count how many birthdays have passed.
How is age handled for a February 29 birthday?
Your exact age in years, months, and days is computed normally. For the next-birthday countdown in a year that is not a leap year, February 29 is treated as March 1, so there is always a next birthday to count toward.
Can I find my age on a past or future date?
Yes. The 'age as of' date defaults to today, but you can set it to any date to see how old you were, or will be, on that day.
Why might my age change by a day around midnight?
The 'as of today' date uses your device's local calendar date. Depending on your time zone, the local date and the UTC date can differ for a few hours around midnight, which can shift the computed age by one day.
What does 'total months' mean?
It is your full age expressed only in months: years multiplied by twelve plus the leftover months, ignoring the extra days. It is useful for ages of infants and young children.