Age Calculator: Find Your Exact Age Online

How This Age Calculator Works

The age calculator subtracts your date of birth from today’s date, or any date you choose, in years, months and days. When a column is too small, it borrows the real number of days in the previous month, so leap years and 28, 30 and 31-day months are all handled correctly. It then converts the same span into total months, weeks and days, and counts down to your next birthday.

You can also use this online age calculator for a date in the past or future: for example, to find how old someone was on their wedding day, or how old you will be on a trip next year.

Which Age Calculator Do You Need?

How to Calculate Age by Date of Birth (Manual Method)

1. Write both dates as year, month and day. For example, today 2026-10-31 and birth 1994-12-15.
2. Subtract the days. 31 − 15 = 16 days.
3. Subtract the months. 10 − 12 is negative, so borrow 1 year (12 months): 22 − 12 = 10 months.
4. Subtract the years. After borrowing, 2025 − 1994 = 31 years.

The answer is 31 years, 10 months and 16 days. If the days column is negative, borrow the number of days in the previous month instead. The age calculator above follows exactly these steps, and our step-by-step guide shows more worked examples.

Why Different Age Calculators Give Different Answers

Two online age calculators can disagree by a day or two. Some treat every month as 30 days or every year as 365.25 days, which is quick but not exact. Others count the end date as an extra day. Our age calculator uses real calendar months and does not count the end date, which matches how birthdays, forms and most standardized tests work.

Age is also counted differently in some cultures. The traditional Korean system, for example, treats a baby as one year old at birth, though South Korea adopted the international method for official use in 2023. This calculator always uses the international method.

Common Uses for an Age Calculator

• Forms and applications, such as passports, insurance and job applications that ask for age on a set date.
• Eligibility checks, for school entry, sports leagues, retirement or age-restricted services.
• Birthday planning, to see how many days are left until the next birthday and which weekday it falls on.
• Health and development, where doctors and therapists need an exact age in months or days.

Age in Different Units

Most people think of age in years, but other units are useful too. Doctors describe babies in weeks and months, tests use years, months and days, and some fun facts use total days. A 30-year-old, for instance, has lived about 360 months, 1,565 weeks or 10,957 days, depending on leap years. This free age calculator shows all of them at once.

Types of Age

The age on your birth certificate is your chronological age. There are other ways to describe age: biological age reflects how your body is aging, mental age compares ability with age norms, and developmental age describes a child’s skills. Read more in what is chronological age and types of age.

Age Calculator FAQs