Age Calculator
Calculate age from date of birth in years, months, and days, using today or a selected date.
Age Formula
- Age = End Date − Birth Date
- Borrow months and days when the current month/day has not reached the birth month/day.
Total Days
- Total days = difference between dates in milliseconds ÷ one day.
If someone was born on January 1, 2000, the calculator compares that date with today or your selected date.
Enter a date of birth and an optional end date. The calculator counts complete years, months, and days.
Use it for birthdays, forms, age checks, school records, or date planning.
Do not estimate age by subtracting only the years; months and days matter before the birthday has arrived.
Examples
Example 1: Birth Year
Born: Jan 1, 2000
As of: Jan 1, 2026
Example 2: Before Birthday
Born: Dec 10, 2000
As of: May 10, 2026
Example 3: Custom Date
Choose any future or past date
Age updates instantlyWhen to Use This Calculator
- Calculate age for forms
- Check birthday age
- Find age on a past or future date
- Prepare school or work records
- Calculate age in years, months, and days
How It Works
- Enter date of birth.
- Choose the date to calculate age on.
- The calculator counts completed years, months, and days.
Common Mistakes
- Subtracting years only
- Using the wrong date format
- Forgetting leap years are handled by dates
- Choosing an end date before birth date
Related Calculators
Frequently Asked Questions
How does the age calculator work?
It compares date of birth with the selected date and counts complete years, months, and days.
Can I calculate age on a future date?
Yes. Choose the future date in the second field.
Does it account for leap years?
Yes. The browser date system accounts for real calendar dates.
Can I leave the second date blank?
Yes. The calculator will use today automatically.