Age Calculator
Calculate your exact age, next birthday countdown, zodiac sign and life statistics
Defaults to today. Change to calculate age at any past or future date.
How Age Is Calculated
Age is calculated by comparing your date of birth to today's date (or any date you specify). The years component counts complete years since birth. The remaining months and days are calculated from the last birthday to the current date, accounting for varying month lengths and leap years.
For example, someone born on 31 January who we check on 28 February has completed 0 months and 28 days since their last birthday in that period — not 1 month, because February is shorter than January.
How Age Is Actually Calculated
Built and verified by Andrius R. · Updated June 2026
"How old are you?" sounds like the simplest question in math — until you try to program it. Calendar months have different lengths, leap years exist, and different cultures don't even agree on when counting starts. Here's what this calculator does and why.
The calendar method (what this tool uses)
Born 15 March 1990, today 10 June 2026:
- Years: 2026 − 1990 = 36, and 10 June is past 15 March, so full years = 36.
- Months: from 15 March to 15 May is 2 full months → 2 months.
- Days: 15 May to 10 June (15 May → 31 May is 16 days, +10) = 26 days.
Result: 36 years, 2 months, 26 days. The subtlety: "one month" isn't a fixed number of days — it means "the same day number in the next month" — so the days component depends on which months the span crosses.
Why "age in days" doesn't divide evenly back into years
Someone exactly 36 by calendar has lived 36 × 365 plus roughly 9 leap days — about 13,149 days, not 13,140. If you need precise day counts (medication schedules, legal deadlines, astronomy), count days directly rather than converting from years. Our date difference calculator does exactly that.
Born on 29 February?
Leap-day babies ("leaplings") get a true calendar birthday only every four years — with a further wrinkle: century years aren't leap years unless divisible by 400 (2000 was; 2100 won't be). For legal purposes, jurisdictions pick a convention: in non-leap years, the UK and Taiwan treat the birthday as 1 March, while New Zealand treats it as 28 February. So a leapling can legally age a day apart depending on the country they're standing in.
Not every culture counts the same way
- International (Western) age — born at 0, +1 on each birthday. What this calculator computes.
- Korean age (historical) — born at 1, +1 every New Year. A baby born on 31 December turned "2" the next day. South Korea officially standardized on international age in June 2023, retiring this system for most legal and everyday use.
- East Asian reckoning — similar one-at-birth systems historically existed in China and Japan and still surface in traditional contexts (the Chinese "nominal age", xusui).
- Horse racing — racehorses in the Northern Hemisphere all "turn a year older" on 1 January regardless of foaling date.
Age milestones around the world
| Age | Common significance (varies by country) |
|---|---|
| 16 | Driving (US, most states); end of compulsory schooling in some countries |
| 18 | Majority/voting in most of the world; drinking in UK/EU |
| 21 | Drinking age (US); historical "key to the door" majority |
| 65–67 | Typical state pension / Social Security full-benefit window, rising in many countries |
Fun calculation this tool makes easy: your 10,000th day lands at about 27 years 4½ months, and your billionth second at about 31 years 8½ months.
// Leap Year Birthdays
People born on 29 February only have a "true" birthday every 4 years. In non-leap years, most celebrate on 28 Feb or 1 March.
// Age Worldwide
In South Korea, everyone is 1 at birth and gains a year on New Year's Day — so Koreans are typically 1–2 years older by Korean reckoning.
// Oldest Person
The verified oldest person ever was Jeanne Calment of France, who lived to 122 years and 164 days (1875–1997).
// Life Expectancy
Global average life expectancy is about 73 years. Japan leads at ~84 years; women live ~5 years longer than men on average globally.