How to use the age calculator
Pick a date of birth and the date you want to measure age on – today is filled in automatically, but you can choose any past or future date. The calculator returns the exact age in years, months and days, together with the total number of months, weeks, days and approximate hours lived. It also tells you the day of the week you were born on and how many days remain until the next birthday.
How age is calculated
Age is counted in completed units. First the calculator counts how many full years have passed since the birth date, then how many full months since the last birthday, and finally the remaining days. When the day of the month on the target date is smaller than the birth day, one month is "borrowed" and replaced with the actual number of days in the previous month. This mirrors the way people naturally state their age and handles months of different lengths and leap years correctly.
Leap-day birthdays
People born on 29 February only see their exact birthday every four years. In non-leap years, the legal birthday is usually treated as either 28 February or 1 March depending on the country. This calculator counts full years from the birth date and treats the next birthday in a non-leap year as 1 March.
Uses for an age calculator
- Checking eligibility for school enrollment, sports leagues, pensions or retirement plans.
- Filling in forms that ask for age in completed years or months.
- Working out the age of a pet, a building, a company or a historical figure.
- Planning a milestone celebration such as 10,000 days alive.
Different cultures count age differently. In the traditional East Asian system, for example, a baby is one year old at birth. This calculator uses the international convention, where age starts at zero and increases on each birthday.
Frequently asked questions
How do I calculate my exact age?
Count the full years since your birth date, then the full months since your last birthday, then the remaining days. The calculator does this automatically.
Can I calculate age on a future date?
Yes. Change the "Age on this date" field to any date after the birth date.
How are leap years handled?
The calculation uses real calendar dates, so leap years and month lengths are accounted for automatically.
What day of the week was I born?
Enter your birth date and the result shows the weekday under "Born on a".
Last reviewed 2026-10-27. This age calculator is provided for general information; verify important decisions with a qualified professional.