Age Calculator
Exact age in years, months, days — plus countdown to next birthday.
How Age Is Calculated
This calculator returns completed years, months and days — the way we conventionally say someone is "32 years, 4 months, and 17 days old." The total-units row also gives raw counts (days, hours, minutes), which can be fun for milestone birthdays: 10,000 days old ≈ age 27.4, 1 billion seconds ≈ age 31.7, 1 million minutes ≈ age 1.9. The Wikipedia article on age covers different cultural conventions for counting age.
Famous landmark numbers
| Milestone | Age (approx) |
|---|---|
| 1,000 days | 2.74 years |
| 10,000 days | 27.4 years |
| 20,000 days | 54.8 years |
| 30,000 days | 82.1 years |
| 1 billion seconds (10⁹ s) | 31.7 years |
| 1 million minutes | 1.9 years |
| 500 weeks | 9.58 years |
| 1,000 weeks | 19.2 years (~end of teens) |
| 2,000 weeks | 38.3 years |
| 4,000 weeks | 76.6 years — Oliver Burkeman's framing of a human lifespan |
Oliver Burkeman's bestseller "Four Thousand Weeks" uses the staggering fact that an 80-year life contains only ~4,170 weeks to argue for ruthless prioritization. A useful reframe — days feel infinite, weeks feel finite.
Cultural Age Conventions
Most Western cultures use "international age" — completed years since birth. But several other systems exist:
- East Asian age (traditional Korea, China, Vietnam): newborns are 1 year old at birth; everyone ages by 1 on Lunar New Year. Can be up to 2 years older than international age.
- Korean reform (2023): South Korea legally adopted international age in June 2023, ending centuries of "Korean age" for official purposes.
- Pregnancy gestational "age": counted from last menstrual period, so a newborn is officially 40 weeks old at birth — see our due date calculator.
Quirks of Date Math
February 29 babies (leap-day or "leaplings") legally turn one year older on March 1 (or February 28, depending on jurisdiction) in non-leap years. Their exact birthday only recurs every 4 years (with adjustments — see the Wikipedia leap year article: century years like 1900 weren't leap years, but 2000 was).
Simple day-subtraction doesn't always give intuitive results because months vary in length (28-31 days) and leap years exist. This calculator handles month/day borrowing correctly using JavaScript's built-in date math.
Frequently Asked Questions
Why does someone born on December 31 turn another year older a day later than someone born January 1?
Because their birthday literally falls one day later. The Dec 31 baby turns 25 on Dec 31; the Jan 1 baby turns 25 on Jan 1 of the next year. Tiny difference, but it matters for legal age cutoffs (school enrollment, drinking age, voting).
Can I calculate my age in another planet's years?
Multiply your Earth age by the inverse of that planet's orbital period in Earth years. Mars year = 1.88 Earth years, so age × (1/1.88). Mercury year is 0.24 Earth years, so age × (1/0.24) = age × 4.17. NASA has an official "your age on other planets" tool.