ConverterHub

Age Calculator

Enter a birth date and get the precise age in years, months and days.

How it is calculated

The tool subtracts the birth date from the target date part by part: years = Ty − By, months = Tm − Bm, days = Td − Bd. If the day difference is negative, one month is borrowed and the length of the month before the target month is added to the days. If the month difference is then negative, one year is borrowed and 12 months are added. Total days is the real elapsed time divided by 86,400 seconds and rounded down; total weeks is total days divided by 7, rounded down. If you leave the target date empty, today's date is used. A target date earlier than the birth date gives no result.

Worked example

As of 16 October 2026, with birth date 1990-05-15 and the target date left empty (so today is used). Years: 2026 − 1990 = 36. Months: 10 − 5 = 5. Days: 16 − 15 = 1. None is negative, so no borrowing is needed. The age is 36 years, 5 months and 1 day, which is 13,303 days or 1,900 full weeks. Run on a later day, the same birth date gives a larger result.

Try this example →

Common mistakes

  • Leaving the target date empty and expecting the age on a past or future date: an empty target means today.
  • Reading the months and days as totals. They are the remainder after the full years, not the whole age expressed in months.
  • Swapping the two dates. A target earlier than the birth date returns nothing.
  • Expecting the weeks figure to include a part-week: it is rounded down to complete weeks only.

About this calculator

This calculator counts the exact span between a birth date and any chosen reference date, breaking the result down into years, months, and days rather than just a rough year count. Doing this by hand is trickier than it sounds because of varying month lengths and leap years, which the calculator accounts for automatically.

It is used to fill in forms that require a precise age, to check eligibility for age-restricted services, and simply to satisfy curiosity about exactly how many days old someone is or how long until a milestone birthday. Parents also use it to track a baby's age in weeks or months during the early stages of development.

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