🎂 Age Calculator

Enter your date of birth and an optional "as of" date to calculate your exact age in years, months, and days — the international age system used worldwide for legal and medical purposes.

Age Results

Age

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International age (years)

Exact Duration — Total Days Lived — Total Weeks Lived — Total Months Lived — Day of Week Born — Next Birthday — Days Until Next Birthday —

Related Tools

Want the Korean age & counting-year age too? Try the Korea age calculator

GUIDE

Learn more

What Is International Age?

International age (sometimes called "Western age") starts at 0 on the day you're born and increases by one on each birthday. It's the legal age standard in most countries, and since June 28, 2023 it is also the sole legal age standard in South Korea.

How Age Is Calculated

Age = reference year − birth year (minus 1 if the birthday hasn't occurred yet)

Example: born May 15, 1990, reference date July 10, 2026 → the birthday (5/15) has already passed this year, so the age is 36.

Days, Weeks, and Months Lived

Beyond your age in years, this calculator shows exactly how many days, weeks, and months you've been alive — handy for celebrating milestones (like your 10,000th day) or tracking a baby's age in months.

Next Birthday Countdown

The calculator finds the closest upcoming birthday from your reference date and counts down the days remaining. If this year's birthday has already passed, it automatically rolls forward to next year.

Frequently asked questions

What's the difference between international age and Korean age?

International age increases on your birthday each year, while the traditional Korean age system starts at 1 at birth and adds a year to everyone on January 1st. Since June 28, 2023, South Korea's legal age has been unified to international age. For the Korean age and counting-year age too, see the "Related Tools" link below to the Korea age calculator.

Can I use a reference date other than today?

Yes. Enter any date in the "as of" field to calculate age and the next-birthday countdown relative to that date — useful for checking your age at a past or future point in time.

How is total days lived calculated?

It's the exact calendar day count from your date of birth to the reference date, automatically accounting for leap years.

What happens if the result would be negative?

The calculator requires the reference date to be on or after the date of birth — it can't compute an age for a reference date earlier than the birth date.