Age calculator

Find your age and days lived from your birth date.

Date of birth As of (default: today)

Pick your date of birth.

Forms want an age, not a birth year, and the answer changes depending on whether the birthday has already happened this year. It is an easy thing to get wrong by one.

This calculator takes a date of birth and returns the age in completed years as of any date you choose, along with the total number of days lived since birth.

How it works

What you enter

Field	Meaning
Date of birth	The birth date. Future dates cannot be selected.
As of	The date to measure the age at. Defaults to today.

Leave the second field alone for a current age, or set it to a future date to check how old someone will be at, say, the start of a school term.

How the age is worked out

This is age by completed years, the standard international method:

Subtract the birth year from the reference year.
If the birthday has not yet arrived in the reference year, subtract one.

So someone born in November 1990, checked in March 2026, is 35 — not 36 — because the birthday is still ahead. A person is zero years old for the whole of their first year, and the number goes up on the birthday itself.

Days lived

The second figure is the plain count of calendar days from the date of birth to the reference date. It ignores the year boundary entirely, so leap days are included as they occur. It is the number behind milestones like a 10,000th day.

Terms explained

Completed years: Age counted by full years finished. The number rises on the birthday, not at New Year.
As of date: The reference date the age is measured at. Defaults to today, but any date works.
Days lived: Total calendar days from birth to the reference date, leap days included.
Date of birth: The starting point of both figures. Future dates are blocked by the picker.

Frequently asked questions

How is age calculated in completed years?

Subtract the birth year from the current year, then subtract one more if the birthday has not happened yet this year. That is the international standard, where a newborn is zero and the age rises on each birthday.

Can I check my age on a future date?

Yes. Change the "As of" field to any date and the tool reports the age you will have reached by then. This is useful for eligibility cut-offs, school enrolment, and visa or insurance age bands.

What is Korean age, and does this tool use it?

Traditional Korean age counted a newborn as one and added a year every January 1. South Korea standardised on international age for legal and administrative purposes on 28 June 2023, and this calculator uses that international method.

How do I find out how many days I have been alive?

Enter your date of birth and leave the second field as today. The second line of the result is the total days lived, counted across every calendar day including leap days.

Why does my age change on my birthday rather than New Year?

Because completed-year counting measures full years actually finished since birth. Until the birthday arrives, the most recent year is incomplete, so it does not count yet.