🎂 Age Calculator

How age is counted

This calculator returns your age in completed years, months, and days — the way age is understood almost everywhere. You turn a year older on your birthday, not on 1 January.

The arithmetic is less trivial than it looks, because months have different lengths. Counting from 31 January to 28 February is one month in some conventions and not quite a month in others. This tool resolves month boundaries by calendar date, which matches how people naturally describe age.

Leap years and the 29 February problem

A leap year adds a day every four years, except in century years not divisible by 400. That is why 1900 was not a leap year but 2000 was. The correction keeps the calendar aligned with the solar year, which is about 365.2422 days long.

People born on 29 February — sometimes called leaplings — have a birthday that appears only once every four years. Most jurisdictions treat 1 March as the legal birthday in common years for purposes such as reaching the age of majority, though a few use 28 February. This calculator counts elapsed time rather than applying any particular legal convention.

Where exact age actually matters

Precise age calculation comes up more often than you might expect. Insurance premiums frequently step up at specific ages, and some insurers use "age nearest birthday" rather than "age last birthday", which can shift a quote by a full year.

Pension eligibility, retirement account withdrawal rules, and certain tax reliefs all trigger at exact ages. School admission cut-offs are usually defined by a date rather than a birthday, so two children born days apart can end up a full academic year apart. Visa and residency rules for dependants often specify an exact age on the date of application.

If you need the gap between two arbitrary dates rather than an age, the date difference calculator handles that directly, and days until counts forward to a future date.

Common questions

Why does my age in days seem higher than expected?

Because a year averages 365.25 days once leap days are included. Multiplying your age in years by 365 undercounts by roughly one day for every four years you have lived.

What is the difference between chronological and biological age?

Chronological age is simply time elapsed since birth. Biological age is an estimate of physiological condition based on various markers, and it has no fixed definition. This calculator measures the former.

Does the calculator account for time zones?

It works from calendar dates rather than exact moments, so it does not adjust for the time zone you were born in. For everyday purposes this makes no difference.