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Age calculator from date of birth

Enter a birth date to get the exact age, totals and the next birthday countdown.

How Age calculator works

Age Calculator takes a birth date and today's date (or a custom reference date you choose) and returns the exact age in years, months and days. The breakdown is precise: if someone was born on 15 March 1990 and today is 10 June 2025, the result is 35 years, 2 months and 26 days. All arithmetic runs in your browser tab; nothing you type is collected or transmitted.

The calculation walks the calendar from the birth date to the reference date. Years are counted by reaching the same calendar day in later years, months by counting full calendar months beyond the last birthday year, and the remaining days by counting from the last month anniversary to the reference date. This means the result correctly reflects variable month lengths: the month count for someone born on 31 January is based on the last day of shorter months, not on a fixed 30-day approximation.

Written by Bastien Sulyan

How to use Age calculator, step by step

  1. Enter the birth date in the date of birth field.
  2. Leave the reference date set to today, or change it to a specific past or future date.
  3. Read the age displayed in years, months and days.
  4. Optionally note the total days lived shown below the main result.

Common use cases

  • A parent wants to know their child's exact age in months for a pediatric appointment that records developmental milestones.
  • An HR administrator needs to verify whether an employee has reached the minimum age threshold on a specific date.
  • A historian wants the exact age of a historical figure at the time of a documented event.
  • Someone wants to calculate the age they will be on a future date, such as their next milestone birthday.

Frequently asked questions

How does the tool count months when someone was born on the 31st?

The month count advances each time the calendar date reaches the same day-of-month as the birth date. For months shorter than the birth day, the tool uses the last day of that month as the anniversary. A person born on 31 January has their monthly anniversary on 28 or 29 February, 31 March, 30 April and so on.

Can I calculate the age at a date in the past or future?

Yes. Change the reference date field to any date you want. The tool calculates the age as of that date, which is useful for historical research or for knowing what age you will be at a future event.

Does the calculation account for leap years?

Yes. A person born on 29 February has a birthday only on 29 February in leap years. In common years, the tool uses 28 February as their birthday for the purpose of counting full years.

Is my date of birth stored or sent when I use this tool?

No. The birth date you enter is processed entirely within your browser's JavaScript engine. It is not sent to any server, not stored in any database, and not retained after you close or refresh the page.

What does 'total days lived' mean in the result?

It is the flat count of calendar days from the birth date to the reference date, including leap days. This is the simplest single-number representation of an age, sometimes used in medical or legal contexts where a day-count is required. The same result panel also gives the weekday you were born on and the number of days until your next birthday.

Can the tool tell me the age of an organisation, brand or building, not just a person?

Yes. The tool is simply a date arithmetic engine; the 'birth date' can be any founding, opening or creation date. Enter the founding date in the date of birth field and it will return the age of whatever entity that date represents.

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