Age calculator

Find out your exact age in years, months, days, weeks, and more.

Date of birth

Age at date

Select your date of birth to calculate your age.

How age is calculated here

Age is counted in whole years elapsed, the convention used almost everywhere for legal and administrative purposes. The calculation takes the difference in calendar years, then subtracts one if the birthday has not yet occurred in the target year. Someone born on 12 September 1990, evaluated on 19 August 2026, is 35 — not 36 — because the birthday is still three weeks away.

Leap days are handled by the calendar itself rather than by an approximation, so the day and month totals stay exact across leap years. This is why a simple divide-by-365 estimate drifts by roughly a day for every four years of age.

Age reckoning is not universal

The whole-years-elapsed method is the international norm, but it is not the only system in use.

System	How it counts	Where
International age	Starts at 0, increments on each birthday	Used almost everywhere, and what this tool reports
East Asian age	Starts at 1 at birth, increments at Lunar New Year	Traditional in China, Korea and Vietnam; now largely ceremonial
Korean “year age”	Current year minus birth year	Common in Korea for school and military cohorts, though South Korea standardised on international age in law from 2023

A person can therefore be described as two different ages on the same day depending on the convention, with the largest gap immediately before a birthday.

What the totals are useful for

The month, week, day and hour breakdowns answer a different question from the year count. Total days is what pension and benefit calculations, visa residency rules and length-of-service awards actually work from. Total weeks is how pregnancy and infant development are tracked. Total hours is mostly a curiosity — though it makes a memorable milestone, since 10,000 days falls a little after the 27th birthday and a billion seconds arrives at roughly 31 years and eight months.

The 29 February problem

Someone born on a leap day has a real birthday only once every four years, and jurisdictions disagree on when they legally turn a year older in common years. Most of the English-speaking world treats 1 March as the operative date; several civil-law countries use 28 February. This tool follows the calendar, which places the birthday on 1 March in non-leap years.

Note too that century years are only leap years when divisible by 400. The year 1900 was not a leap year and 2100 will not be, which is a well-known source of off-by-one errors in date libraries and spreadsheets.

Privacy

The dates you enter stay in your browser. Nothing is submitted, stored or logged, so this is safe to use with a real date of birth — which is more than can be said for tools that post the same information to a server.

Frequently asked questions

Why does the result say 35 when the birth year subtracts to 36?

Because the birthday has not happened yet this year. Age counts completed years, so subtracting birth year from current year overstates age for anyone whose birthday falls later in the calendar.

How are leap years handled?

The calculation works from real calendar dates rather than a fixed 365-day year, so leap days are counted exactly. This is why the day total differs from a naive years times 365 estimate.

What about someone born on 29 February?

This tool follows the calendar, so in non-leap years the birthday falls on 1 March. Legal practice varies — most common-law countries use 1 March, several civil-law systems use 28 February.

Can I calculate age at a past or future date?

Yes. The second date defaults to today but accepts any date after the date of birth, which is useful for eligibility checks and retirement planning.

Is this suitable for legal or official use?

It uses the standard international convention, but for anything binding — pensions, visas, benefits — confirm against the rules of the relevant authority, which may define cut-offs differently.

Is my date of birth sent anywhere?

No. The calculation runs entirely in your browser and nothing is transmitted or stored.

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