Age Calculator
Find your exact age in years, months, and days, with total weeks, days, hours, and a birthday countdown.
Learn how it works: How to Calculate Your Exact AgePick a date of birth to see the exact age.
How to use the age calculator
Choose your date of birth in the first field. The second field starts on today's date, so your current age appears at once, but you can set it to any later date to find your age on a graduation day, an anniversary, or any milestone you have in mind.
The headline gives your age in years, months, and days. Below it you will see the same span counted four other ways, in total months, weeks, days, and hours, along with a countdown to your next birthday.
How age is actually calculated
It is tempting to take the number of days lived and divide by 365, but that quietly drifts. Years are not all the same length, and over a long life the leap days add up, so the shortcut can leave you a day or two off your real age.
This tool counts up the calendar instead. It subtracts the birth date from the target date piece by piece, borrowing from months and years the way you would on paper. When the day of the month does not reach far enough, it borrows the exact length of the preceding month, which is why a 31-day month and a 28-day month are handled differently.
Leap years and February 29 birthdays
A leap year adds February 29 every four years, with the century rule that years divisible by 100 skip the leap unless they are also divisible by 400. The calculator applies that rule, so spans crossing the year 2000 or 2400 stay accurate.
People born on February 29 raise a fair question: when is their birthday in an ordinary year? This tool counts the anniversary as March 1 in non-leap years for the birthday countdown, while the age itself is measured exactly from the original February 29 date.
Why the total figures differ
The years-months-days headline and the running totals describe the same stretch of time from two angles. The headline is a calendar breakdown, while the totals flatten everything into a single unit, so a 36-year-old has lived roughly 432 months or about 13,149 days.
Seeing the span in weeks and hours can be oddly grounding, and it is handy for planning too. Counting in total days, for instance, makes it simple to work out a round-number day milestone like a 10,000-day anniversary.
Frequently asked questions
- How is my exact age calculated?
- The calculator subtracts your birth date from the target date by calendar parts, borrowing the real length of each month rather than assuming 30 days. This gives a precise years, months, and days result instead of an estimate.
- Why not just divide the days lived by 365?
- Because years vary in length once leap days are counted. Dividing by 365 accumulates a small error, so over decades it can report your age a day or two off. Counting the calendar directly avoids that drift.
- How are leap years handled?
- A year is a leap year if it divides by 4, except century years, which must divide by 400. The tool follows this rule, so February has 29 days only in the correct years and the day counts stay exact.
- When is the birthday of someone born on February 29?
- For the next-birthday countdown, a February 29 birthday is treated as March 1 in years that have no February 29. The age itself is still measured exactly from the original leap-day date.
- Can I calculate my age on a future date?
- Yes. Set the second field to any date on or after your birth date to find how old you will be then. The birth date cannot be in the future, since you cannot have an age before you are born.