Life Calculator

Age Calculator

Exact age is not a subtraction. Months have different lengths, so the answer depends on the order you count in.

Last reviewed: Written and checked by the Life Calculator editorial team

1 = January.

How exact age is counted

Age in years, months and days is computed by subtracting each component separately and then borrowing where a component goes negative — exactly like long subtraction, except the “base” for days is the length of the preceding month rather than a fixed number.

years = this year − birth year months = this month − birth month days = today's date − birth date if days < 0: borrow the length of the previous month, months − 1 if months < 0: borrow 12, years − 1

Because months vary from 28 to 31 days, the borrowing step means the answer genuinely depends on which month you are in. This is not an imprecision in the calculator; it is a property of the calendar.

Different legal conventions

Most of the world uses the system above: you are 0 at birth and gain a year on each anniversary. Other systems exist and occasionally matter:

  • East Asian age reckoning. Traditionally a person is 1 at birth and gains a year at Lunar New Year, so someone could be “2” days after being born. South Korea formally moved to international age in 2023.
  • Insurance age. Many life insurers use “age nearest birthday”, which can make you a year older than your actual age for six months of the year.
  • 29 February birthdays. Jurisdictions differ on whether a leapling legally turns a year older on 28 February or 1 March in common years. It affects things like when someone reaches the age of majority.

Why other calculators disagree

Two sources of difference are worth knowing about. The first is time zones: a calculator working in local time can be a day out for someone born on a date boundary. This tool works in UTC throughout, which is consistent even if it occasionally differs from a local-time result by a day.

The second is how months are counted. Counting from 31 January to 28 February is either 28 days or one month depending on which you ask for, and neither is wrong. This calculator reports years, months and days as a decomposition, and total days as an exact count — the second figure is the one to use for anything that must be precise.

Frequently asked questions

How many days old am I exactly?

The 'total days lived' row gives it. It is a straightforward count of days between the two dates and is unaffected by the varying lengths of months, which makes it the most reliable figure on the page.

Why does my age in months seem slightly off?

Because 'total months' multiplies years by twelve and adds the remaining months, which ignores the leftover days. It is an approximation by design. For exact intervals use the total days figure.

Does this handle leap years?

Yes. It works with actual calendar dates rather than assuming 365-day years, so every leap day you have lived through is included in the day counts.