Age Calculator

Age is calculated by subtracting your birth date from today's date, accounting for the varying lengths of months and leap years. This calculator gives your age in complete years, remaining months, and remaining days — the same way official documents (passports, medical forms) define age. For example, if you were born on March 15, 2000 and today is January 10, 2025, you are 24 years, 9 months, and 25 days old.

To find how many days old you are, subtract your birth date from today and count the total calendar days. A 30-year-old is approximately 10,950 days old (30 × 365.25 accounting for leap years). Enter your birth date above for your precise total days lived.

Leap years add an extra day (February 29) every 4 years, with exceptions for century years not divisible by 400. Over a lifetime, this adds approximately 18 extra days per 75 years. For people born on February 29, their 'exact' birthday only occurs every 4 years — legally, most countries recognize February 28 or March 1 as their birthday in non-leap years.

Subtract the birth year from the current year to get a base age. Then check if the birthday has occurred yet this year: if today is before their birthday this year, subtract 1. For example: born June 15, 1990. Today is January 10, 2025. Base = 2025 − 1990 = 35. Since January 10 is before June 15, their age is 35 − 1 = 34 years old.

Chronological age is simply how many years have passed since your birth — what this calculator measures. Biological age reflects how old your body actually is based on health markers like telomere length, cardiovascular fitness, cellular health, and inflammation levels. Biological age can be significantly younger or older than chronological age depending on lifestyle, genetics, and health habits.

To calculate days until your next birthday, find the date of your upcoming birthday this year (or next year if it's already passed) and subtract today's date. This calculator does it automatically and shows your next birthday date alongside the countdown.