Age Calculator

How to use the age calculator

1. Enter the date of birth. Use the date picker or type the date. Any date from the year 1800 onwards works.
2. Check the "age at" date. It starts as today's date on your device. Change it if you need an age on a particular day, such as the closing date of an application, a school entry cut-off or a future anniversary.
3. Read the results. The main result is the exact age in years, months and days. Below it you can see the same period in total months, weeks and days, the date of the next birthday and how many days remain until it, and the day of the week of the birth date.

The tool also works for any two dates, not only birthdays. Use it to find how long someone has worked somewhere, how old a business is or how long ago an event happened.

How the exact age is worked out

Counting an age sounds simple, but months have different lengths, so "one month" is not a fixed number of days. This calculator uses the same method most people use when they count on a calendar:

1. Count the whole years that have passed since the birth date. A year is complete on the birthday itself.
2. From the last birthday, count the whole months. A month is complete on the same day number in a later month.
3. Count the remaining days from that point to the end date.

For example, someone born on 15 May 1990 is 36 years, 5 months and 7 days old on 22 October 2026. The 36th birthday was 15 May 2026, five whole months later is 15 October 2026, and there are 7 more days to 22 October.

Month-end and leap-year dates

When the start date is near the end of a month, a later month may not have that day. Not every month has a 31st, and February usually has only 28 days. In that case the calculator counts the month as complete on the last day of the shorter month. So from 31 January, one month is complete on 28 February (or 29 February in a leap year).

The same rule applies to people born on 29 February. In years without a 29 February, this calculator treats 28 February as the birthday, so the next age is reached at the end of February. Some countries and organisations use 1 March instead for legal purposes. If an exact legal age matters, for example for a licence, a pension or a contract, check the rule that applies where you live.

Total days, weeks and months

The total number of days is the exact count of calendar days between the two dates, including every leap day in between. The end date is not counted as an extra day, in the same way that a person is 0 days old on the day they are born. Total weeks is the number of days divided by 7, with the leftover days shown separately. Total months is the number of whole months, followed by the remaining days.

Useful ways to use an age or date calculator

• Checking whether someone meets an age limit on a specific date
• Working out the age of a child for school, sports or travel forms
• Counting how many days are left until a birthday or anniversary
• Finding the length of employment, a lease or a membership
• Seeing which day of the week you were born on

Some cultures count age differently. In some traditional systems a baby is one year old at birth, for example. This tool uses the international convention in which age starts at zero and increases on each birthday.

Want the full explanation? Read our guide: How to calculate age exactly (with leap years and month ends).