Age Calculator
Exact age in years, months and days, and the countdown to the next birthday.
Age looks like subtraction and is not. Months have different lengths, February changes size every four years, and the answer depends on whether the birthday has already passed this year. This calculator does the counting properly, gives the total in days, weeks and hours as well, and tells you when the next birthday falls and on which weekday.
How it works
Enter the date of birth
Any date in the past.
Choose the reference date
Today by default, but it can be any date — useful for eligibility checks.
Read the breakdown
Years, months and days, plus the totals and the next birthday.
Why age is not a subtraction
Ask how old someone born on 31 January is on 1 March, and there is no single correct answer. Counting whole months gives one month and one day if you treat 28 February as the month’s end, or one month and two days if you count from the 31st onward into a month that has no 31st. Different jurisdictions and different software resolve this differently.
This calculator uses the convention almost everyone means: count whole years first, then whole months, then the remaining days, borrowing from the length of the preceding month when the day of the month has not yet been reached. It is the same method a person uses counting on a calendar, and it produces answers that match how ages are stated in ordinary speech.
The total in days is a separate calculation and does not divide neatly into the years-and-months figure. Someone aged exactly 30 has lived either 10,957 or 10,958 days depending on how many leap years fell in that span. Both numbers are correct; they answer different questions, which is why both are shown.
Leap years, and the people born on 29 February
A leap year is not simply every fourth year. Years divisible by 100 are skipped, unless they are also divisible by 400 — which is why 1900 was not a leap year and 2000 was. The rule exists because the Earth takes about 365.2422 days to orbit the Sun, and the plain four-year rule overcorrects by roughly three days every four centuries.
Around one person in 1,461 is born on 29 February, and in three years out of four their birthday does not occur. Most legal systems settle this by treating 1 March as the anniversary in common years; a few, including parts of New Zealand and Taiwan, use 28 February instead. This calculator follows the 1 March convention and says so when the birth date is a 29 February.
The distinction matters wherever an age threshold has legal weight — a driving licence, a pension entitlement, an insurance band. In most of the world a person legally becomes a given age on the anniversary itself; in traditional East Asian age reckoning the count starts at one and increases at new year, so the same person can be two years older by that measure. If an official form asks for an age, it is asking for the anniversary count this tool produces.