Age calculator
Your exact age in years, months and days — and the number of days you have been alive, counted properly across leap years and clock changes.
How old exactly?
Runs in your browser. Nothing is sent anywhere and there is nothing to sign up to.
| Age | — |
|---|---|
| Total days | — |
| Total weeks | — |
| Total months | — |
| Next birthday | — |
| Day you were born | — |
Why ages disagree between calculators
Two things make age arithmetic slippery, and most tools get at least one wrong.
The first is months are not equal. Counting "one month" from 31 January lands on a date that does not exist. The convention used here is the calendar one: the month count increases when the day-of-month is reached, and the remaining days are counted against the length of the previous month. That is how the law treats age, and how you would count it out loud.
The second is clock changes. If you subtract two dates in local time and divide by 86,400,000, a span crossing the March clock change is 23 hours short and a span crossing October is an hour long. Over a year that is enough to round a day the wrong way. Everything here is computed in UTC, where every day is exactly 24 hours.
Leap years
A year is a leap year if it divides by 4, except centuries, except centuries dividing by 400. 2000 was a leap year; 1900 was not; 2100 will not be. Anyone born on 29 February has a legal birthday of 1 March in England and Wales in non-leap years, which is why the day count here is the more useful figure for them than the anniversary.
Common questions
How do I work out my exact age?
Count whole years to the most recent birthday, then whole months to the same day-of-month, then the remaining days. This tool does that in UTC so leap years and clock changes cannot shift the result.
How many days have I been alive?
The total days figure above. It counts every calendar day between the two dates, including leap days, and excludes the end date.
Why does another calculator give a different answer?
Usually because it counts a month as 30 days rather than as a calendar month, or because it subtracts local timestamps and loses an hour at a clock change. Both produce answers that are off by a day or two over a lifetime.
What day of the week was I born?
Shown above. It is derived from the date itself rather than looked up, so it is correct for any date the browser can represent.
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