Age Calculator

Type in a birth date and you get the exact age right away: years, months, and days, not the rough "days over 365" guess that drifts off by a day around every birthday. It counts age the way a person actually does, walking the real calendar with the right month lengths and leap years. You also get the totals in weeks, days, hours, and a live seconds counter, the weekday you were born on, and the countdown to your next birthday.

But the one thing this does that most age calculators skip entirely is sitting right below, so I'm leading with it.

If your baby arrived before their due date, their age comes in two flavors, and mixing them up is a common worry for new parents. There's the age counted from their birthday like anyone else, called chronological age. And there's corrected age, which counts from when they were actually due.

Corrected age is the one pediatricians use to check a premature baby's development. A baby born eight weeks early who is six months old chronologically is only about four months corrected, and that four-month number is what matters when you're looking at milestones like rolling over, sitting up, or a first smile. Judge a preemie against their chronological age and a perfectly on-track baby can look behind, which is a scare nobody needs.

To get it here, tick "Baby born early" and enter how many weeks early the baby came. The tool subtracts those weeks and shows the corrected age next to the chronological one. Doctors generally use corrected age until around age two, after which the gap stops mattering. If your pediatrician tracks it a little differently, go with what they tell you. This is just here to give you the number fast, and spare you one small worry.

Chronological age is the plain one: the span from the birth date to the date of the test, written as years, months and days. It is the number psychologists, speech and language therapists, occupational therapists and school assessors need before they can score anything, because the norm tables inside a standardised test are keyed to age bands measured in years and months. Land in the wrong band and the score that comes out is wrong, however carefully the test itself was given. Examiners often write the figure with semicolons, 8;4;15 for eight years, four months and fifteen days, so nobody can misread it as a date.

That is exactly what the three numbers at the top of this page are, in that order. Put the date of birth in the first box, put the date of testing in "Age on date", and read them left to right. It walks the real calendar instead of dividing days by 365, so it borrows the right number of days from the right month, and a February 29 birth is handled deliberately rather than quietly.

Two limits worth knowing before a number goes onto a protocol. Some manuals round the days off, drop them, or carry their own rule for a test given across two sittings, so follow the manual wherever it says something different from this. And this page stops at the age. Reading that age into the right row of the norm table is still yours to do, because no scoring program lives here.

1. Enter the date of birth. Yours, a family member's, a public figure's, or the start date of anything that ages.
2. Leave "Age on date" blank for age as of today, with the seconds ticking live.
3. Or set a target date to find the age on a specific day, past or future. A school cutoff, a wedding, how old someone was at some event.
4. Read the exact age up top, plus the weekday you were born and the countdown to your next birthday.
5. Switch to "Age difference" to enter two birth dates and see the exact gap between two people, and who's older.
6. Tick "Baby born early" for a corrected age. Then copy the result, or share a link that reopens your exact entries, birth date included, which the Share row tells you before you copy it.

Age looks like plain subtraction until you try it by hand, because months are different lengths and February gains a day every four years. The tidy "days over 365" shortcut quietly drifts off by a day or two around each birthday, because a year isn't exactly 365 days and those leap days add up.

This one skips the shortcut and follows the actual calendar. It counts full years birthday to birthday, then full months, then the leftover days, borrowing the right number of days from the correct preceding month. That's why the answer matches how your age reads on a form, an application, or a legal document, instead of being close but off. A February 29 birthday is handled too. Common years have no February 29, so this tool puts the birthday on March 1, which is the reading US and UK practice generally take, and a leap-day baby still ages one year at a time. One quirk falls out of that and the page says so on the day: measured on March 1 the age reads a day past the anniversary, because the months and days part counts from February 28, the last day of the birth month.

Sometimes you don't want years and months, you want the raw count. How many days you've been alive, how many weeks along something is, how many hours. It shows the same span every way at once: months, weeks, days, hours, minutes, and that live seconds counter ticking while the page is open. Fun to watch, and genuinely useful when you want to know exactly how many days sit between now and a deadline.

The age-difference mode is the other handy one. Enter two birth dates and it gives you the exact gap, down to the day, and tells you who's older. Good for the "wait, how far apart are we really" question, or working out the spacing between siblings.