Age Calculator
Enter a date of birth and any target date to get an exact age — years, months, days, plus total days and weeks lived.
How the age calculator works
An age calculator answers a deceptively simple question: how much time has passed between the day someone was born and another date? Counting whole years is easy, but an exact age — years, months and days — needs care, because months have different lengths and leap years add an extra day every four years.
The method mirrors column subtraction. First the years are subtracted, then the months, then the days, borrowing from the next column whenever a value would go negative. If the target date's day-of-month is smaller than the birth day, we borrow the length of the previous month; if the target month is earlier than the birth month, we borrow twelve months from the year count.
Worked example: someone born on 15 March 1990, measured on 20 October 2026. Days: 20 − 15 = 5. Months: 10 − 3 = 7. Years: 2026 − 1990 = 36. Their exact age is 36 years, 7 months and 5 days — and they have been alive for 13,368 days.
Beyond birthdays, exact ages matter for school admissions, sports age groups, pension eligibility, insurance, and legal thresholds such as voting or driving ages — all situations where 'about 36' is not good enough.
Frequently asked questions
How is exact age calculated?
Your exact age is found by subtracting your date of birth from the target date, then borrowing days and months where needed — just like subtracting numbers column by column. If the target day is earlier in the month than your birth day, one month is borrowed; if the target month is earlier in the year than your birth month, one year is borrowed.
Can I calculate someone's age on a future date?
Yes. Choose any 'age at date' — for example a school enrolment cut-off, a wedding day, or a retirement date — and the calculator works out the age the person will be on that day.
Does the age calculator count leap years correctly?
Yes. The calculation uses real calendar dates in your browser, so February 29 birthdays and leap years are handled exactly, with no 365.25-day approximations.
What is my age in days?
The result includes your total days lived, which is simply the number of days between your birth date and the target date. It is a fun number for milestone birthdays such as your 10,000th day.