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Age calculator

Work out an age in years, months and days from a date of birth, with the total in months, weeks and days, the weekday you were born on and how long until the next birthday.

The dates

Today by default. Change it for an age at any other date.

Age

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Enter a date of birth to see the age.

How an exact age is counted

Take the whole years first, then the whole months that are left, then the days. Someone born on 15 March 1994, counted to 22 September 2026, has had 32 birthdays; from 15 March 2026 there are six whole months to 15 September; and then seven days. So: 32 years, 6 months and 7 days.

The order is not arbitrary. Counting the days first and dividing them into months gives a different answer, because months are not all the same length. Working from the largest unit down is what makes the answer match how people actually say an age.

Why the totals do not divide into each other

Only the day count is exact. It comes from converting both dates to a continuous day number and subtracting, so every leap day in between is included and nothing is rounded. The months, weeks and years are all measured against that, which is why dividing the total days by 30 will not reproduce the months figure.

There is deliberately no age in hours. A day is 24 hours except where the clocks change, when it is 23 or 25, and an exact figure would also need the time of birth. Multiplying days by 24 produces a number that looks precise and is quietly several hours out.

Leap days, and the birthday that mostly is not there

A person born on 29 February has a real birthday roughly once every four years. The common convention, and the one used here, is that the anniversary falls on 28 February in other years, so the birthday stays inside the right month. Several jurisdictions use 1 March instead, on the reasoning that the day after 28 February is the day after the birthday.

Neither is wrong; they are different rules. Where it matters legally, coming of age, a licence, an insurance band. The rule that counts is the one in your own jurisdiction, so check it rather than taking the date from any calculator.

Counting to a date other than today

The second field starts at today but takes any date. Set it back to find how old someone was when something happened, or forward to find an age at a wedding, a school start or a retirement date. Set it before the date of birth and the tool says so rather than reporting a negative age, which would be arithmetic rather than an answer.

Questions

How is an exact age worked out?
Count the whole years from the birth date to today, then the whole months left over, then the days. Born on 15 March 1994 and counting to 22 September 2026 gives 32 years, then 6 months to 15 September, then 7 days. The order matters: counting days first and converting to months gives a different and wrong answer, because months are not all the same length.
Why do the totals not divide into each other?
Because only the day count is exact. An age of 32 years and 6 months is not 390 days times anything, since months run from 28 to 31 days and leap years add a day. Every total here is measured from the day count rather than converted from the years-and-months figure, so they will not always agree with a rough conversion you do by hand.
When is the birthday of someone born on 29 February?
It depends who is asking. This calculator moves it to 28 February in common years, which is the usual convention and the one most registries follow. Some jurisdictions use 1 March instead, New Zealand and parts of the United States among them, so for anything legal, check the rule that applies to you rather than taking the date here.
Does this count leap days?
Yes. The day count comes from converting both dates to a continuous day number, so every leap day between them is included automatically. A year spanning 29 February is 366 days here and an ordinary year is 365.
Why is there no age in hours?
Because it would not be right. A day is 24 hours except where clocks change, when it is 23 or 25, and an age in hours also depends on the time of day you were born, which this tool does not ask for. Multiplying days by 24 would produce a precise-looking figure that is quietly wrong by several hours. The day count is exact, so that is what is shown.
Can I work out an age at a past or future date?
Yes. The second field is set to today, but you can change it to any date, how old someone was when something happened, or how old they will be at a wedding or a deadline. If you set it before the date of birth, the tool says so rather than showing a negative age.
How do I find my age in a specific number of days or weeks?
The results show the total days and the whole weeks with any leftover days. For a milestone in the other direction, the date you turn 10,000 days old, say, use the date add and subtract calculator and add that many days to your birth date.
Is this the same as my age in the Islamic calendar?
No. A Hijri year is about eleven days shorter than a Gregorian one, so a lunar age runs ahead by roughly one year every thirty-three. If you want that figure, the Islamic age calculator works it out and shows both side by side.

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