🎂 Age Calculator
Calculate your age in years, months, and days from your date of birth. Compare ages relative to today or to a custom reference date. Supports batch CSV uploads for multiple birthdates.
Single Age Calculation
Result: -
Batch Mode (CSV Upload)
Upload CSV lines like:
birthdate,refdate
1990-03-18,2025-09-23
2000-01-01,
How Age is Calculated
Age is simply the difference between two calendar dates: the date of birth and a reference date (often today). But in practice, calculating age correctly must account for calendar irregularities: leap years, months of different lengths, and cultural differences in age reckoning.
1. Standard Western Age
Most countries define age as the number of full years since birth. A person born on 2000-01-01 will be 25 years old on 2025-01-01, even if not yet 25 years + months. This method is used legally in most jurisdictions.
2. Detailed Breakdown
Our calculator also provides months and days for precision. Example: Born 2000-01-01, reference 2025-09-23 → 25 years, 8 months, 22 days.
3. Leap Year Handling
People born on February 29 celebrate only every 4 years. Age calculators handle this by considering March 1 as the birthday in non-leap years when calculating full years.
4. Weeks & Days
Sometimes age is expressed in weeks or total days. Useful in medicine (tracking infants), project planning, and scientific studies.
5. Applications
- Healthcare: Growth charts, dosing by age.
- Legal: Eligibility (driving, voting, pensions).
- Education: School admissions, cut-off dates.
- Sports: Age categories for competitions.
6. Cultural Variations
In Korea, a traditional system added one year at birth and incremented at New Year. International age is now standard, but some cultural reckoning persists.
7. Worked Examples
Example 1: Birth: 1990-03-18, Today: 2025-09-23 → 35 years, 6 months, 5 days.
Example 2: Birth: 2000-02-29, Reference: 2025-03-01 → 25 years, 0 months, 1 day.
8. FAQs
Can I calculate age on any past date?
Yes, use the "Reference Date" field.
Why do leap-year birthdays matter?
Because Feb 29 doesn’t exist every year, calculators adjust to March 1 in non-leap years.
How is age in months calculated?
By subtracting full years first, then months, then days.
Can this show total days lived?
Yes — many calculators add this metric; you can extend the script easily.
9. Conclusion
Age calculators save time and avoid mistakes in date arithmetic. Whether for personal, legal, or scientific purposes, precise age calculations matter.