What it does
This calculator works out an exact age from a date of birth: how many whole years, months and days separate two dates. Enter a date of birth and, optionally, the date to measure the age at — leave the second box on today and it tells you how old someone is right now. It also gives the total span as a number of weeks and days. Everything is worked out in your browser; no dates are sent anywhere.
How it works
Age is counted the way people actually say it: full years first, then the leftover whole months, then the leftover days. The tricky part is that a "month" is not a fixed length — February has 28 or 29 days, while others have 30 or 31. So the calculator subtracts day-from-day, month-from-month and year-from-year, then borrows when a column comes out negative.
If the day-of-month you are measuring at is earlier than the day you were born on, there aren't yet a full month's worth of days, so it borrows the length of the previous calendar month and drops the month count by one. If the months then go negative, it borrows twelve months from the year count. The total-days figure is counted directly between the two calendar dates, and total weeks is simply that divided by seven, rounded down.
Worked example
Take a birth date of 1990-06-15 measured at 2024-06-30. Subtracting gives 34 years, 0 months and 15 days. In total that is 12434 days, which is 1776 whole weeks.
Common uses
- Forms and eligibility: giving your exact age in years and months where a form or application asks for it.
- Pets and milestones: working out a pet's age, or a baby's age in weeks and days.
- Time since an event: how long ago something happened, counted to the day.
- Anniversaries: checking how many full years have passed since a date.
Frequently asked
How do I calculate my exact age?
Enter your date of birth and leave the second date on today. The calculator subtracts the two dates and borrows across months and years so the result reads as full years, then months, then days.
How many days old am I?
The result line shows a total-days figure alongside the years/months/days breakdown — that is the count of whole days between your birth date and the date you are measuring at.
How is a leap-year birthday handled?
If you were born on 29 February, the anniversary in a non-leap year falls on 1 March, since February has only 28 days that year. The calculator borrows the real length of each month, so the count stays correct across leap years.
Why isn't "one month" always 30 days?
Calendar months vary from 28 to 31 days, so the breakdown counts real months rather than fixed 30-day blocks. That is why two ages with the same number of total days can show slightly different month-and-day figures.
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