Age Calculator
Exact age in years, months, days, and more.
The Age Calculator tells you exactly how old you are in years, months, and days, plus total days, weeks, and hours lived — and how many days until your next birthday.
How Age Is Calculated Exactly
Years, months, and days
Age is found by subtracting the birth date from the target date step by step. First, full years are counted. Then remaining full months. Then leftover days. Each step borrows from the previous unit when the subtraction would go negative, so the result is always exact.
Leap years and month lengths
Because months have different lengths (28–31 days) and leap years add an extra day in February, a simple division cannot give exact results. The calculator handles both automatically. People born on February 29 have their birthday counted on February 28 in non-leap years.
Common uses
Exact age is needed for age verification, medical age requirements, retirement eligibility, legal documents, and birthday apps. You can also calculate age at any past or future date by entering a custom target date in the second field.
Age = Target date − Birth date (accounting for leap years and month lengths) Frequently Asked Questions
How do I calculate my exact age in days?
Subtract your birth date from today's date to get the total number of days. The calculator does this automatically and shows total days in one of the result cards.
What happens if I was born on February 29?
In non-leap years, your birthday is counted on February 28. The calculator handles this automatically so your age is always correct.
Can I calculate how old I will be on a future date?
Yes. Enter your date of birth, then enter any future date in the optional second field. The calculator will show your exact age on that date.
How many days until my next birthday?
The last result card shows the number of days until your next birthday based on today's date. If today is your birthday, it shows 'Today!' and counts to next year.
Is this calculator accurate for very old or very young ages?
Yes. The calculator uses JavaScript Date objects that handle centuries of dates correctly. It works for any birth date from historical records to recent births.
What is the formula for the Age Calculator?
Age = Target date − Birth date, broken into full years, then remaining months, then remaining days. Total days = (Target date − Birth date) in milliseconds divided by 86,400,000. Weeks = total days divided by 7. Hours = total days multiplied by 24.