Age Calculator
Find an exact age in years, months and days from any date of birth — plus the total number of days, weeks and hours lived. Enter a birth date and, optionally, the date to measure to.
How age is calculated
Age is the time elapsed from a date of birth to a reference date (today by default). The calculator counts complete years first, then the remaining whole months, then the leftover days — borrowing from the next unit up exactly the way a calendar does.
It also gives running totals: the total days, weeks and hours since birth, which are handy for milestones and trivia.
Frequently asked questions
How do you calculate age from a date of birth?
Count the full years between the birth date and today, then the remaining whole months, then the leftover days. The calculator does this with real calendar months, so the result matches how people state their age.
Can I find my age on a future or past date?
Yes. Change the “Age at” date to any date and the calculator measures the age at that moment instead of today.
Why do months have different lengths?
Calendar months range from 28 to 31 days, so the day remainder is measured against the actual month involved — that is why age in months and days is exact rather than approximate.