Age Calculator
Calculate your exact age in years, months, and days from your date of birth. See total days old, weeks old, and days until your next birthday.
Formulas, assumptions, and rounding are documented in our calculator methodology.
How Age Is Calculated Step by Step
1. Count complete years from birth year to current year, adjusting back one year if the birthday has not yet occurred this calendar year. 2. Count complete months from the birth month to the current month within the final partial year. 3. Count remaining days from the birth day-of-month to today within the final partial month. 4. For total days old, count every day from the birth date to today, including all leap days.
Leap Years and Age Calculation
A leap year occurs every 4 years (years divisible by 4), except century years (1800, 1900, 2100) are not leap years unless also divisible by 400 (2000, 2400 are leap years). This means the average year is 365.2425 days. Over 30 years, this adds roughly 7–8 extra days compared to counting exactly 365 days per year. The difference matters for precise day-count calculations like this one.
Frequently Asked Questions
- Exact age is calculated by finding the number of complete years elapsed since the birth year, then the number of complete months in the remaining partial year, then the remaining days. This accounts for varying month lengths (28–31 days) and leap years.
- This calculator shows your total age in days by counting every day from your birthdate to today, correctly accounting for all leap years in between. The number grows by 1 each day and by 366 rather than 365 in leap years.
- If you were born on February 29, your birthday in non-leap years is conventionally celebrated on either February 28 or March 1. Legal and official age calculations in most countries count February 28 as your birthday in non-leap years. This calculator uses February 28 as the leap-day birthday for non-leap years.
- This calculator uses calendar dates without time-zone adjustment. If you were born near midnight in a different time zone, your official age in your current location may differ by one day from what this calculator shows. For official documents, use the date on your birth certificate.