Last updated:
Find your exact age in years, months and days from your date of birth, check how old you’ll be on a future or past date, see how many days remain until your next birthday, or compare the ages of two people. All calculations use full calendar dates, so leap years and different month lengths are handled correctly.
How to use the Age Calculator
Enter a date of birth to see the exact age. To find an age on a past or future date, change "Calculate age as of" to that date instead of today. Use "Next birthday" to see how many days remain until the next birthday, or "Age difference" to compare two people's dates of birth.
How age is calculated
This calculator does not simply subtract the birth year from the current year, which gives the wrong answer whenever the birthday hasn't happened yet in the current year. Instead, it works out the full number of complete years, then the full number of complete months left over, then the remaining days, using the actual calendar dates involved.
How to calculate age from date of birth
Compare the day and month of birth with the day and month on the target date. If the target day of the month is earlier than the birth day of the month, borrow a month (and use the correct number of days in the previous month, since months are not all the same length). If the result is a negative number of months, borrow a year. What is left is the exact age in years, months and days.
Exact age in years, months, and days
For example, someone born on 15 June 2000 is 25 years, 11 months and 30 days old on 14 June 2026, because their birthday hasn't happened yet that year, and becomes exactly 26 years old on 15 June 2026.
How to calculate age on a specific date
Set "Calculate age as of" to any date, past or future, rather than leaving it as today. The same calendar-based method is used, so you can check how old someone was on a specific historical date, or how old they will be on a future date such as a graduation, retirement or contract deadline.
How many days old am I?
The total days figure counts every calendar day between the date of birth and the date you're calculating as of, including both leap days that have occurred in that span. It is an exact count, not an estimate.
How many weeks old am I?
Total weeks is the total number of days divided by 7. Because a lifespan is rarely an exact multiple of 7 days, this is normally shown with a fraction of a week, which is expected and not an error.
How to find your next birthday
The next birthday mode looks at today's date and the date of birth's month and day, and finds the next time that month and day occurs, whether that's later this year or, if the birthday has already passed this year, next year instead.
Age difference between two people
To compare two people, enter both dates of birth. The calculator treats whichever date is earlier as the starting point and works out the calendar-exact years, months and days between the two, regardless of which one you type first.
Leap years and February 29 birthdays
Someone born on 29 February only has a real birthday in leap years. In the years between, this calculator's next-birthday feature shows 28 February as the practical date, which is the most common convention. The exact-age calculation still works correctly in every year, including leap years, because it compares full calendar dates rather than counting birthdays.
Common age calculation mistakes
- Subtracting birth year from the current year only. This is wrong whenever the birthday for this year hasn't happened yet, and it can overstate the age by a full year.
- Treating every month as 30 or 31 days when converting days to months. Real months vary in length, and using a fixed number produces the wrong month-and-day breakdown.
- Ignoring time zones when comparing dates and times together. This calculator compares calendar dates directly, avoiding the off-by-one errors that time-zone conversions can cause.
Real-world uses of an age calculator
- Filling in forms or applications that ask for your exact age or date of birth.
- Checking someone's age on a specific date, such as the start date of a course, contract or policy.
- Working out how many days or weeks old a baby is.
- Planning ahead for an upcoming birthday.
- Comparing the ages of two people, such as siblings, a couple, or colleagues.
Age-related rules for school enrollment, employment, or eligibility for a product or service vary by country and organization. This calculator gives you the exact age; always check the specific rule that applies to you with the relevant official source.
Frequently asked questions
How do I calculate my age?
Enter your date of birth into the exact age mode. It compares your birth date with today's date, using full calendar years, months and days, not just a subtraction of years.
How is exact age calculated?
By comparing the year, month and day of birth with the target date, carrying over a month or year where the day or month of the target date comes before that of the birth date. See "How age is calculated" above for the full method.
Can I calculate my age on a specific date?
Yes. Change "Calculate age as of" to any past or future date, and the calculator will show the exact age on that date instead of today.
How many days old am I?
The exact age mode shows total days lived as an exact count of every calendar day since birth, including leap days.
How do I calculate age from date of birth?
Enter the date of birth and the target date, then compare them year by year, month by month and day by day, borrowing a month or year where needed. This calculator does that automatically.
How does the calculator handle February 29 birthdays?
The exact age calculation compares full calendar dates, so it is accurate in every year. For the next-birthday countdown, non-leap years show 28 February as the practical birthday date.
Can I calculate the age difference between two people?
Yes, use the age difference mode and enter both dates of birth. It works out the calendar-exact years, months and days between them.
What is chronological age?
Chronological age is simply the amount of time that has passed since someone's date of birth, expressed in years, months and days. It's the everyday meaning of "age", as opposed to other specialized measures used in some medical or developmental contexts.
Can I calculate a future age?
Yes. Set "Calculate age as of" to a future date to see how old someone will be on that date.
Why is my age different from simply subtracting birth years?
Subtracting birth years only works if the birthday for the current year has already happened. If it hasn't, that method overstates the age by one year. This calculator checks the actual month and day, not just the year.