How to use
- Pick your date of birth from the calendar or type it in.
- The reference date is set to today by default. If you want your age on a different day — a job application cutoff, a wedding, a retirement date — change it there.
- Press Calculate. Your age in whole years appears in large type, with the exact years-months-days breakdown, next-birthday countdown, and total days lived below it.
- Use Copy result to paste the summary into a message or note.
How age is calculated
Chronological age — the system used almost everywhere today — starts at 0 on the day you're born and increases by one on each birthday. The formula is simple:
Age = reference year − birth year (subtract 1 if this year's birthday hasn't happened yet; on the birthday itself, the new age applies).
The exact breakdown goes one step further: it counts the full years, then the full calendar months since your last birthday, then the leftover days. Someone born on March 15, 2000 is, on August 2, 2026, exactly 26 years, 4 months, and 18 days old.
How age is counted in different cultures
It hasn't always been this simple. Under the traditional East Asian counting system — historically used in Korea, China, Japan, and Vietnam — a baby was considered 1 year old at birth, and everyone gained a year together at New Year, not on their individual birthdays. A child born in late December could be "two" within a couple of weeks. Japan moved to chronological age by law in the 1950s, and South Korea, where the old "Korean age" persisted in everyday life the longest, officially standardized on chronological age in June 2023. If a Korean friend once gave you an age one or two years higher than you expected, that's why.
| System | Age at birth | When it increases | Example: born Dec 31, 2000, on Jan 2, 2001 |
|---|---|---|---|
| Chronological (international) | 0 | On each birthday | 0 years old |
| Traditional East Asian counting | 1 | At New Year, all at once | 2 years old |
Leap-year birthdays
Roughly 1 in 1,461 people is born on February 29 — a date that only exists in leap years. For every other year, a convention is needed: this calculator (like the law in most places) rolls the birthday to March 1 in non-leap years, while a few jurisdictions use February 28 instead. Either way, leap-day babies get their "real" birthday only once every four years, which makes for excellent birthday-party math: a 24-year-old leap-day baby has had just six actual birthdays.
Good to know
- Milestone planning: set the reference date to a future birthday to see the countdown, or find the exact date you turn 10,000 days old — days lived is a surprisingly fun number to track.
- Forms and eligibility: many applications ask for your age "as of" a specific date. Enter that cutoff date as the reference date instead of today.
- Half birthdays: the months-and-days breakdown makes it easy to spot when you're exactly X years and 6 months — popular for kids' celebrations.
- The "in months" figure divides your days lived by the average month length (30.44 days), so it's an approximation — handy for infants, whose age is usually given in months.
Results are for reference only. For legal or administrative matters that hinge on an exact age, follow the definition used by the relevant authority.
Frequently asked questions
How is exact age calculated?
Age in years equals the reference year minus the birth year, minus one if this year's birthday hasn't arrived yet. You turn a year older on your birthday itself. The months-and-days breakdown then counts full calendar months since the last birthday, with the remaining days on top.
What if I was born on February 29?
In non-leap years this calculator treats March 1 as the birthday, which is the convention used in many jurisdictions (others, such as parts of the US, use February 28). Your real birthday still only comes around every four years — a favorite bit of trivia for leap-day babies.
Do all cultures count age the same way?
No. Most of the world uses chronological age, where you are 0 at birth and gain a year each birthday. Traditional East Asian reckoning worked differently: in Korea's old counting system you were 1 at birth and everyone aged together on New Year's Day, so a baby born in late December could be "two years old" within days. South Korea standardized on chronological age in 2023.
Can I calculate my age on a date other than today?
Yes. The reference date defaults to today, but you can change it to any past or future date — useful for checking how old you were on a specific day or how old you'll be at retirement, on a form's cutoff date, or at a future event.
Is my date of birth stored anywhere?
No. All calculations run in JavaScript inside your browser. The dates you enter are never transmitted to a server or saved.