Age Calculator
Work out your exact age in years, months, and days — or in total weeks, days, and hours — plus the weekday you were born and a countdown to your next birthday.
“How old are you?” has a fuzzier answer than it sounds — months have different lengths, leap years add days, and “26 and a half” hides the details. This calculator gives the precise answer: your age in years, months, and days, the same age re-expressed in total months, weeks, days, and hours, the weekday you were born, and exactly how long until your next birthday.
How exact age is counted
The calculator counts the way birthdays do:
- Whole years — complete trips around the calendar from your birth date.
- Whole months — complete calendar months past your last birthday.
- Days — whatever’s left, borrowed from the actual length of the month involved.
That borrowing step is why naive “divide by 365.25” math drifts: from January 31 to March 1 is one month and one day in calendar terms, not 29.5 ÷ 30.4 of something. Exact date math has to walk the real calendar — this tool does.
Fun with the totals
Re-expressing an age in single units turns up milestones the year count hides: your 10,000th day lands around age 27.4, your 1,000th week just past 19, and a billion seconds — about 31.7 years — is a legitimately celebrated “gigasecond birthday.” The totals rows give you the raw numbers to find yours.
Leap-day birthdays
Born February 29? Your calendar birthday appears once every four years (2024, 2028, …). For the in-between years this calculator uses February 28 — the common convention — so the countdown and “turns N on” rows always have a concrete date. Legally it varies by place: some jurisdictions roll leap-day birthdays to March 1 instead.
Frequently asked questions
How is exact age calculated?
The calculator counts whole calendar years first, then whole months, then leftover days — the way birthdays actually work. Because months differ in length, the day count borrows from the real calendar month, so the result is exact for any pair of dates.
What is chronological age?
Chronological age is simply the time elapsed since birth — what this calculator measures. The term distinguishes it from 'biological age' estimates based on health markers. Schools, sports, and clinics all use chronological age, usually expressed in years and months.
How does it handle February 29 birthdays?
If you were born on February 29, your birthday exists only in leap years. In other years the calculator uses February 28, the common civil convention — some places (like New Zealand law) use March 1 instead, so leaplings get to choose in practice.
Can I calculate age at a date other than today?
Yes — set the 'age on this date' field to any date: a past date for age at an event, or a future date to see how old you'll be. It also shows the age in total months, weeks, days, and hours, which is handy for milestones like a 10,000th day.