Age Calculator

What "your age" actually means

Your age in years is straightforward, but the breakdown underneath — "X years, Y months, Z days" — is surprisingly subtle. This calculator uses the convention most civil systems use: subtract the birth date from today, rolling over if today's day-of-month is earlier than the birth day-of-month, and counting a month as whatever length the calendar assigns it. That gives the same answer as what a UK passport office, a US driver's licence application, or a school enrolment form would use.

If you were born on 31 March and today is 30 April, you are zero months and 30 days old this month — not one month, because 31 doesn't exist in April yet. Some calculators get this wrong and report "1 month, -1 day". This one uses calendar arithmetic (the same algorithm dayjs, date-fns, and Java's ChronoUnit use) to avoid that.

Leap years and the 29 February edge case

A year is a leap year if it's divisible by 4, except century years, which must be divisible by 400. 2000 was a leap year; 1900 wasn't; 2100 won't be. Someone born on 29 February 2000 gets an official birthday every four years. Most jurisdictions resolve this administratively: England, Wales, and New Zealand treat 1 March as the legal birthday in non-leap years, while Scotland, the US, and most EU countries use 28 February. The calculator just reports the elapsed time; the legal fiction is up to your local laws.

Age thresholds worth knowing

• 13: minimum age for most major social platforms (COPPA / DSA).
• 16: voting age in Scotland, Wales, Austria, and Brazil; consent for medical decisions in much of Europe.
• 18: legal adulthood in most countries; driving, voting, contracts in the UK and most EU.
• 21: minimum legal drinking age in the US and a handful of other countries.
• 25: threshold for rental car companies in many countries; human prefrontal cortex is generally considered mature around here.
• State pension age: 66 in the UK (rising to 67 from 2026), 67 in the US for those born after 1960.

"Korean age" and other counting systems

In East Asian age reckoning you are 1 at birth (because gestation counts as the first year) and everyone ages by one year on New Year's Day rather than on their birthday. Under that system a baby born on 31 December can be "2 years old" by 1 January, even though it's less than a day old. South Korea legally abolished this system for administrative purposes in June 2023 and moved to international age, but it still shows up in daily conversation. If you need "Korean age" take the international age from this calculator and add 1 if you've already had your birthday this year, or 2 if you haven't.

Interesting figures you can read off the result

• Total days lived is handy for the "10,000 days old" trend (≈ 27 years 4 months).
• Heartbeats — at a resting 72 bpm, multiply your minutes lived by 72 for a rough count. A 30-year-old has racked up about 1.1 billion.
• Breaths — about 16 a minute awake, 12 asleep — roughly 20,000 a day.
• Earth laps around the Sun — same as years, which is faintly cosmic if you think about it.

Privacy

Your birth date is entered into a form, read by JavaScript on this page, and used in a subtraction. It is never sent anywhere. If you'd prefer, disconnect your internet after this page loads — the calculation still runs.