Age Calculator
Work out an exact age in years, months and days from a birth date, plus the countdown to the next birthday.
Results are provided as is, for general information. Check anything important before relying on it. See the Terms of Use.
About this tool
Enter a birth date and get the exact age as of today — or any other date you pick — broken into years, months and days, plus the total number of days lived and a countdown to the next birthday. Age counts the way legal and administrative rules do: a year only ticks over on the birthday itself, not at the calendar year change. A Feb 29 birthday is treated as Feb 28 for the countdown in a year that isn't a leap year, then rolls forward to the next real or clamped occurrence. It shares its underlying date arithmetic with the Date Difference tool but is framed around a single birth date, defaults the second date to today, and adds the next-birthday figure that a generic two-date tool doesn't give you.
How it works
Age = full years + full months + remaining days since the birth date Next birthday = the birth date's month and day, in this or next year
Subtract the birth date from the as-of date one unit at a time: whole years first, then whole months, then the days left over. Counting months and days rather than dividing days by 365 keeps leap years from skewing the result.
| Question | Working | Answer |
|---|---|---|
| Born 15 May 1990: how old on 10 March 2025? | 34 years to 15 May 2024 → 9 months to 15 Feb 2025 → 23 days | 34 years, 9 months, 23 days (12,718 days old) |
| How long until the next birthday for that person? | 10 March 2025 → 15 May 2025 | 66 days (15 May 2025) |
When to use it
Questions
Does it count age the way official records do?
Yes — a year of age only counts once the birthday has actually happened, exactly like a passport, a school cutoff or a legal-age check. Someone born on 2010-03-15 is still 15 (not 16) on 2026-03-14, and turns 16 the next day.
Why does a Feb 29 birthday show Feb 28 as the next birthday in most years?
Feb 29 only exists in a leap year, roughly one year in four. In any other year the countdown clamps it to Feb 28 so there's always a concrete next date to count down to, and it lands on the real Feb 29 again whenever the target year is a leap year.
Can I check an age as of a past or future date, not just today?
Yes — the 'As of' field defaults to today but is a normal date picker. Set it to any date to see the age (and days to the next birthday) as of that point instead.
Does this handle time zones?
No, and it doesn't need to — like the Date Difference tool, it works on plain calendar dates (YYYY-MM-DD) with no time-of-day or time-zone component, so there's no DST edge case to worry about.
Why does a Feb 29 birthday show Feb 28 in most years?
Feb 29 exists only in leap years; in all others the birthday is conventionally observed on Feb 28, which is what official systems do — so the countdown clamps to Feb 28 and returns to the real Feb 29 whenever the target year is a leap one. That gives a real next date to count toward rather than a fabricated March-1st compromise. Run through the tool: as of 2026-10-01, someone born 2000-02-29 is 26 years 7 months 3 days, with the 2027 birthday (a non-leap year) 150 days out, on Feb 28.
Can it count ages before 1970 or for very old birth dates?
Yes — the arithmetic is calendar arithmetic on real dates, not timestamp milliseconds, so centenarians and historical figures resolve exactly. The date picker's practical floor is the browser's year range; dates further back can be entered by typing. One caveat for historians: pre-Gregorian dates are computed on the proleptic Gregorian calendar, the standard convention, which diverges from Julian-calendar records before a region adopted the Gregorian reform.
What is the 'total days' figure for?
Administrative counts that run in days rather than years: visa and residency durations, warranty ages, round-number milestone announcements ('10,000 days old'). It is also the raw figure underneath the years/months/days breakdown, derived from the same date arithmetic, so the two can never disagree. For a span between two arbitrary dates rather than birth-to-now, the Date Difference tool expresses the same math more generally.
Does it count age the way passports and forms do?
Yes — a year of age ticks over on the birthday itself: someone born 2010-03-15 is still 15 on 2026-03-14 and turns 16 the next day, not at the calendar year. Historical East Asian reckoning (newborns counted as one, everyone aging at New Year) puts a person one or two years ahead of this figure; the tool computes only the internationally standard birthday-based age.
Why are months in the breakdown, not just years?
Because forms, pediatric charts and insurance questions routinely want '26 years, 7 months, 3 days', not a lone '26'. The breakdown is calendar-exact — real month boundaries with leftover days, matching how a person would count on their knuckles — and the years figure is exact as well, derived from that arithmetic rather than rounded.
Do the dates stay on my device?
Yes — the calculation is pure date arithmetic in your browser, with nothing sent, stored or logged. That matters for age queries more than it seems: a birth date paired with a health, employment or eligibility question is exactly the personal data that should stay local — which is why the whole date-tool family here runs client-side.