An age calculator is a tool that measures the time between a date of birth and another date — today unless you choose otherwise. It returns the exact age in years, months and days, and the same span expressed in months, weeks, days, hours, minutes and seconds. It applies the real length of every calendar month and the full leap-year rule, which is where counting on your fingers usually goes wrong. Nothing is uploaded and there is no sign-up.

Work down the units in order. Subtract the birth year from the target year, then the month, then the day. If the target day is earlier in the month than the birth day, borrow the number of days in the previous calendar month and take one off the month count; if the month is earlier, borrow twelve months and take one off the year count. Someone born on 14 June 1990 is, on 3 September 2026, 36 years, 2 months and 20 days old. Entering both dates above does the same arithmetic instantly.

Type your date of birth into the three boxes and leave “Use today’s date” ticked. Your age appears immediately in years, months and days, with total months, weeks, days, hours, minutes and a live seconds count underneath. To check your age on a different date — an exam day, a policy start date, a deadline — untick that box and enter the date instead.

Your age right now is the time elapsed since the start of your date of birth in your own time zone. Enter your date of birth and the calculator shows it to the second, updating as you watch. A date of birth carries no clock time, so the count runs from midnight at the beginning of that day; if you know your time of birth, your true figure is that many hours lower.

Your real age — your chronological age — is the full years, months and days since you were born, not the current year minus your birth year. Year subtraction is one year too high until your birthday has passed, so enter the complete date to get the real figure. Note that “real age” is sometimes used for biological or metabolic age, which is estimated from health markers and is not something a calendar can work out.

A current age calculator is one that answers “how old am I today?” rather than asking for two dates. This page works that way by default: “Use today’s date” is ticked, so the target date follows your device clock and the result stays correct the next time you open it. Untick it and the same tool becomes a two-date calculator for any past or future date.

The calculator subtracts your date of birth from the target date one unit at a time. It takes the difference in years, then months, then days. If the day of the month has not been reached yet it borrows the length of the previous calendar month — so someone born on 31 January is one month old on 28 February, not zero months and 28 days.

A leap-year birth date has no anniversary in a common year. This calculator follows the most widespread civil convention and treats 1 March as the birthday in non-leap years, which is the rule used in England and Wales, Hong Kong and most of the United States. New Zealand and Taiwan use 28 February instead. Your age in whole years is the same under either rule on every other day.

Because it is measuring against the current moment rather than against midnight. The count starts from midnight at the beginning of your birth date in your own time zone, since a date of birth carries no clock time. If you set a custom “age on” date, the counter shows the whole-day total instead.

Decimal age expresses age as a single number, such as 8.42 years. Paediatric growth charts, sports age-grouping and some statistical work use it. This calculator measures the fraction as the proportion of the way through your current birth year, so it lands exactly on a whole number on every birthday — dividing total days by 365.25 does not.

Yes. Untick “Use today’s date” and enter any date. This is how you work out how old a relative was when a census was taken, how old a child was on the first day of a school year, or whether someone met an age threshold on a particular date.

Yes. Switch to “Find date of birth”, enter the age and the date that age applied, and the calculator returns the birth date. Genealogists use this constantly, because headstones and death records usually record an age at death rather than a birth date.

Enter the date of birth and the date the test was administered, then read the years, months and days. Test manuals write that as years;months.days — 7;4.12 is seven years, four months and twelve days. The dedicated chronological age calculator shows the figure in that notation, along with the rounded-to-the-nearest-month version and the flat 30-day manual method, so you can match whatever your instrument asks for.

No. Everything runs in your browser. The date appears in the page URL so you can bookmark or share the result, but nothing is uploaded, stored on a server or used for advertising.

Enter the baby’s date of birth and leave “Use today’s date” ticked. Read the weeks-and-days row for the first few months — that is the unit health visitors, vaccination schedules and growth charts use — and the months-and-days row after that. For a premature baby, work out the corrected age by entering the due date instead of the birth date; both figures are usually recorded side by side for the first two years.

Enter the date of birth, untick “Use today’s date”, and enter the date of death: the years, months and days shown are the age at death. If you have it the other way round — an age at death from a record or a headstone, but no birth date — switch to “Find date of birth” and enter the age with the date of death. There is also a “Find date of death” mode that returns the date on which a given age would have been reached.

Roughly. Subtracting the birth year from the current year gives the age someone turns during this calendar year, which is one year more than their real age until their birthday passes. If the exact day matters — eligibility, test scoring, legal thresholds — enter the full date. Where only the year is known, entering 1 July gives the smallest average error.

The birth-date panel shows the next birthday’s date, the weekday it lands on and the number of days to go, all counted from today in your own time zone. To check a birthday further out, untick “Use today’s date” and enter that birthday as the target date.

A search engine answer box gives you whole years and stops there. This page gives the exact years, months and days, the same span in weeks, hours, minutes and ticking seconds, decimal age, the next-birthday countdown, milestone dates, and reverse modes that solve for a date of birth or a date of death. It also works on any target date rather than only today, and the result stays in a shareable URL.

Pick whichever matches how you normally write dates. The format only changes the order of the input boxes on screen — each box is labelled Day, Month and Year, so the calculation cannot be thrown off by an ambiguous date like 04/05/2001.

Enter your child’s date of birth, untick “Use today’s date” and enter the date you are asking about — the first day of term, a school cut-off date, a flight, a birthday party. The result gives their age on that date in years, months and days, and in weeks for the early years. This is also how you check whether a child will have turned a required age by a fixed deadline.

Schools set a minimum age as at a fixed cut-off date, not as at the day you apply — commonly 31 March or 1 June of the admission year, with LKG usually requiring around three and a half to four years completed. So enter your child’s date of birth, untick “Use today’s date”, and enter the cut-off date printed in the prospectus; the years and months shown are the age the school will assess. Always take the exact cut-off and minimum from the school or state rules, as both vary.

Enter your date of birth and read the total-days figure, which counts every calendar day from your birth date to the target date, leap days included. The same panel gives the total in months, weeks, hours, minutes and seconds, so round-number days like 10,000 are easy to spot. Ten thousand days is roughly 27 years and 4 months.

Untick “Use today’s date” and enter both dates: the date of birth, or start date, in the first set of boxes and the end date in the second. The calculator returns the gap in years, months and days and in every other unit. It works for any pair of dates, so the same tool covers age at death, length of service, time since an anniversary or the span between two events.

Use DATEDIF against TODAY(): =DATEDIF(A2,TODAY(),"Y") for whole years, and =DATEDIF(A2,TODAY(),"Y")&" y "&DATEDIF(A2,TODAY(),"YM")&" m "&DATEDIF(A2,TODAY(),"MD")&" d" for years, months and days. The formulas table in the guide above lists the variants for months, weeks and days, and for a fixed end date in place of TODAY().