Age Calculator
An age calculator works out your exact age in years, months, and days from a date of birth and a count-up date.
This one also shows the next birthday and the weekday you were born on. The whole formula is published below, the same two dates always give the same age, and the calculation runs in your browser without storing anything.
How to use it
Enter your date of birth
Pick the day, month, and year you were born. The tool accepts any date between 1900 and 2100, including February 29 in leap years.
Set the count-up date
The page already has today's date filled in. Change it to a past or future date if you need your age on a form or announcement date.
Press Calculate
The exact age appears as years, months, and days, followed by total months, weeks, and days. You also see the next birthday and the weekday you were born on.
Check the formula
The page shows how the whole-month count and remaining days are worked out, so you can repeat the arithmetic by hand and get the same result.
Share the result card
Create a shareable image with your age in years, months, and days; neither of the dates you entered appears on it. The image is drawn in your browser; no details are added to a link.
How your exact age is calculated
The calculator starts with the date of birth and the count-up date. It works out the largest number of whole calendar months that can be added to the date of birth without passing the count-up date. If adding a month would land on a day that does not exist in that month, it uses the last day of that month instead.
The remaining days after those months are then counted. Years are the whole months divided by 12, and the leftover months are the remainder. It also gives total months, total weeks rounded down, and total days.
For the next birthday, the calculator finds the smallest N of at least 1 where the date of birth plus N years is on or after the count-up date. That N is the age you will turn. A February 29 birthday in a non-leap year is treated as February 28.
If the count-up date is the birthday itself, the result says today and the age has already changed. The weekday of the date of birth is shown too. The same two dates always produce the same age, because the calculation is fixed arithmetic with no random element and no time-zone adjustment.
Age on a specific date
The second date field is the date you want the age to be counted up to. It comes pre-filled with today's date, but you can change it to any date from 1900 to 2100. This is useful when a form, application, or announcement asks for your age as of a particular date.
The result then shows your exact age on that date, not on the day you opened the page. If the chosen date is earlier than your date of birth, the tool asks you to check the dates. The arithmetic is the same whatever date you pick: whole calendar months first, then the remaining days.
The same birth date and count-up date will always give the same result.
Questions people ask
How is exact age calculated in years, months and days?
The tool finds the largest number of whole calendar months you can add to the date of birth without passing the count-up date. If that lands on a date that does not exist, it uses the last day of the month. Years are those months divided by 12, the remainder becomes months, and any days left after that are counted separately. The full formula is shown on this page.
How do I find my age on a specific date?
Set the second date field to the date you need, such as the date on a form or announcement. The page automatically fills in today's date, but you can change it to any past or future date between 1900 and 2100. The result then shows your age on that date, not on today. The same calculation is used regardless of which date you pick.
What if I was born on February 29?
In a non-leap year, the calculator treats your birthday as February 28. When it adds a year to a February 29 date, it lands on February 28 in years without a February 29, then continues from there. On a leap year, the birthday is February 29 itself. The next birthday and age are calculated from that adjusted date.
Why can two people born a day apart show different months?
Because whole calendar months are counted first, not a fixed number of days. Months have different lengths, so adding one month from January 31 goes to February 28 or 29, while from February 1 goes to March 1. Two birth dates one day apart can therefore land on different month counts even though the total number of days is close.
Which day of the week was I born on?
The result shows the weekday of your date of birth. It is calculated from the date itself using a standard calendar algorithm, so it works for any date between 1900 and 2100. You can check it against any calendar or weekday calculator; the answer will match. The weekday is displayed next to the age result.
Is my date of birth stored anywhere?
No. The calculation runs in your browser, and the dates you type stay in your browser and are not sent to us or stored on any server. There is no sign-up, no account, and no hidden transfer. When you close the tab, the date of birth is gone. A share image you create is drawn in your browser and does not include your date of birth.
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