How Age is Calculated

This age calculator calculates age in years, months and days given a date of birth. You can also use the age calculator to find length of time between two dates.

For convenience the calculator gives results in many different units of time. You can find age in years, months and days, or months and days.

If you wanted to know "How many weeks have I been alive?" or "How many days have I been alive?" this calculator shows the answer in total weeks and total days. We also calculate age results in total hours, total minutes, and total seconds.

What is My Age?

This chronological age calculator can help you calculate your age. Input your date of birth and today's date to find your current age. You can also input a different end date to see what your age would be on that day. You can see how many days are left until your next birthday or event date at the bottom of all age calculations.

How Old is My Child?

Parents of newborn babies or infants often need to count weeks or months to tell someone how old their child is. This calculator automatically provides weeks and months of age for any age calculation.

To find how many weeks old your newborn is, input their date of birth and click the Calculate button. The "Find Age on" boxes automatically include today's date but you can also input a date in the future. The calculator displays your child's age in weeks, and also months if applicable.

How Age is Calculated

This age calculator uses two methods to calculate age. One calculates age in years, months and days, and also months and days. The other method precisely calculates age in total days only to provide that solution to you.

In the first method, the age calculator finds age in general terms. It counts all years as 365 days. It also treats all months as an average of 30.4167 days.

We divide 365 by 12 to get the average 30.4167 days per month. The calculator then finds the time between two dates in standard-length years and months.

For example, a teenager might say he is 15 years old. He would not say that he's 12 normal years old plus 3 leap years old.

This age calculator uses the same assumption. We know years can be different lengths. However we treat regular years and leap years as equal. The same is true for months, where each month is a generic month that is 30.4167 days long.

These assumptions won't work in the calculation to find the total number of days. In this case the calculator uses a programming function to find the exact number of days since a date of birth or event. This function counts the regular years and leap years in a time span. The age calculator then converts that time span into days.

Calculate age in total number of days as the sum of:

• Number of years, x, with 365 days = 365 * x plus,
• Number of leap years, y, with 366 days = 366 * y plus,
• Number of days in the remaining partial year

The age calculator also finds the specific number of days in a partial year. For example, if you were born on March 5 and today is June 7, the calculator calculates the days between those dates. The answer includes the number of years, months and days since your birth.

How Many Days Until...?

If you want to calculate by hand how many days until some date or event, you need to account for extra days in leap years. You also need to know the months with 31 days, those months with 30 days, and the one month with 28 days.

Number of Days per Month

Common Age Milestones

Different cultures celebrate various age milestones. Here are some common ones:

• 1 year - First birthday
• 13 years - Becoming a teenager
• 16 years - Sweet sixteen (in many Western countries)
• 18 years - Legal adulthood in many countries
• 21 years - Full legal adulthood in the United States
• 40 years - Often considered a significant milestone
• 50 years - Half-century
• 65 years - Traditional retirement age
• 100 years - Becoming a centenarian