Birthday Calculator

1. Calculate an exact age based on date of birth
2. Find out when your next birthday is
3. Find out how old you are
4. Calculate what year were you born
5. Calculate date of birth from age and birthday
6. Find date of birth from age on a given date
7. How to determine the DoB of a deceased person

    Calculate an exact age based on date of birth

This online birthday calculator makes it possible to calculate the precise age of a person to the day, given the date of birth (a.k.a. DoB) is known with the same precision. Just enter the birthday date and press calculate to see how many full years, months, weeks, and days have elapsed since the date of birth.

If you want to see how old you will be at any given point in the future, or how old were you on a specific date in the past, simply enter that date in the second input field before pressing the calculation button.

    Find out when your next birthday is

This birthday calculator can also be used to determine the date of your next birthday as well as how many days until it comes. If you are asking yourself how long until your next birthday party or "when is my birthday?", then using the tool is an easy way to find out without doing any time difference math yourself.

The date of birth calculator can be used to find the time you have to plan a birthday party for a friend or relative as well. Obviously, you need to know their date of birth, or at least the month and day of the month (if unsure of the year of birth, enter any year prior to the current year).

    Find out how old you are

The answer to this question may be somewhat complicated if an exact solution is sought. This birthday age calculator is based on the way human age is calculated in most Western countries. According to it a person who was just born has an age of 0 years, 0 months, and 0 days. The age consequently becomes 1 year, 0 months, and 0 days exactly a year from their birth. This would be on their first birthday. Consequently the second birthday is when a person becomes two years of age, and so on.

Sometimes a person would cite their complete age as in the example above, and that is straightforward enough. However, sometimes one would say their running age, which is the current age plus one, which may make the answer ambiguous. Citing a chronological age with completed years, months, and days is the most accurate answer one can give to the question "How old are you?".

    Calculate what year were you born

That question can be answered easily if you know your current age, accurate to the year. It's like asking "If I'm 18 what year was I born?". If you are 18 this year, then you were born in either 2008 or 2007, depending on whether or not you've already had your birthday in 2026. That is because the birthday event shifts the math by one year.

To further narrow it down, you need to know how old you were at the beginning of the current year. If you were 18, then you were born in 2007. If you were still 17 years old instead, then you were born in 2008 and would turn 18 this year.

Another way to simplify the finding of a birth year is to take the age one becomes this year instead of thinking of whether you've had your birthday or not. For example, if you turn 16 this year, your year of birth is 2010 (2026 - 16 = 2010).

    Calculate date of birth from age and birthday

A common example is when you know when a given person's birthday is (or was), and you know how many years they will become (or were) on that date. With a known birthday date and age, estimating the date of birth is a simple task of subtracting the given number of calendar years. This is something a DoB calculator can be used for.

For example, you know Bob is about to turn 30 on his birthday which is on May 12, 2026 and you want to figure out when he was born. To do this, simply subtract 30 years from 2026 and then add the date and month which remain unchanged. In this case 2026 minus 30 equals 1996, consequently he was born on May 12, 1996. The result can be checked using our date of birth calculator above.

    Find date of birth from age on a given date

In another example, if you know the age of a person on a given date, the date of birth can be calculated from that. With a known date and age, estimating the birth date is a simple task of subtracting the given number of calendar years, months and days of age. The more precisely you know the age, the more precise the DoB calculation by age will be.

For example, if you know Alice was exactly 15 years, 6 months, and 3 days old on Sep 5, 2026 you can calculate her date of birth by subtracting her age from Sep 5, 2026. In this case 2026 minus 15 equals 2011 and Sep is the ninth month so 9-6 = 3. Mar is the third month, and subtracting 3 days from 5 equals 2, meaning her birth date is Mar 2, 2011. If we had only known the age approximately, say just the years and months, we would have only been able to calculate the date of birth approximately, to within a month.

    How to determine the DoB of a deceased person

In genealogy, one may sometimes be interested in determining the date of birth (DoB) or the year of birth of a deceased person for which the known information is only the date on which death occurred, as well as their approximate age in years, or sometimes years and months. Computing an approximate date is then a task of time subtraction, the outcome of which would be as precise as the accuracy with which the age of the person is known. Our birth year calculator can perform the time calculations for you.

For example, if it is known only that the person was 65 years old at the time of their passing, then the date of birth can be determined only approximately, with up to a year of difference. If the age is known more precisely, the DoB can be calculated more accurately.