Age Calculator
Calculate exact age in years, months, weeks, and days from any date of birth.
Plus hours alive, life percentage, day of week born, and milestones.
The age calculator computes the exact difference between your date of birth and a target date (today by default), then breaks it into useful units — years, months, weeks, days, hours, minutes — plus a few interesting derived numbers.
How It’s Calculated
The math is straightforward subtraction with calendar awareness:
Age = Target Date − Date of Birth
The tricky part is handling varying month lengths (28 to 31 days) and leap years. A leap year has 366 days; the rule is “divisible by 4, except centuries, except centuries divisible by 400.” So 2000 was a leap year, 1900 was not, 2024 is.
What Each Output Means
- Years, months, days — your precise chronological age
- Total days alive — the raw count from birth to target date
- Total hours, minutes, seconds — same number expressed at finer granularity
- Day of week you were born — the calendar weekday of your birth
- Life percentage — what fraction of an 80-year average lifespan you’ve used. Don’t take this too seriously — actual life expectancy varies by country, sex, and lifestyle, and the average is steadily increasing.
- Days until next birthday — countdown to the upcoming anniversary
Useful Things You Can Do With This
- Verify your exact age for a legal document or application
- Calculate someone’s age on a specific past or future date (curious how old you’ll be at retirement? Set the target to that year)
- Find out how many days until a wedding anniversary or milestone birthday
- Compute the age difference between two people — calculate each separately, then subtract
Worked Example
Born March 15, 1990. Target date: March 26, 2026.
- 36 years, 0 months, 11 days
- 13,160 days alive
- 315,840 hours
- About 18.95 million minutes
- Born on a Thursday
- ~45% of an 80-year lifespan
- 354 days until next birthday
A Note on Legal Age
Most jurisdictions consider you a year older starting on the anniversary of your birth date — not the day after. East Asian “Korean age” works differently: you’re 1 at birth and gain a year every Lunar New Year. Don’t confuse the two when crossing borders.
Worth Knowing
The Gregorian calendar (the one most of the world uses) was introduced in 1582 and replaced the Julian calendar. Birth dates from before October 1582 in some countries, or as late as 1923 in others, may have been recorded under the Julian system — those calculations get messy. Modern dates are clean.