Age
Calculator

Enter your date of birth using the date picker. The calculator defaults the end date to today, but you can change it to any date to find the exact difference between two dates.

The tool calculates your age by counting complete years from your birth date to the target date, then complete months within the remaining period, then leftover days. This gives you the same result you would get counting on a calendar, properly handling months with 28, 29, 30 or 31 days.

Total days are calculated by finding the difference in milliseconds between the two dates and dividing by 86,400,000 (the number of milliseconds in a day). Total weeks and total hours are derived from the total day count.

The calculator also identifies the day of the week you were born, your Western zodiac sign based on your birth month and day, your Chinese zodiac animal based on the 12-year cycle, and a countdown showing how many days remain until your next birthday.

Knowing your exact age in years, months and days comes up more often than you might expect. Here are the most common situations where a precise age matters in the US.

US law ties specific rights and responsibilities to certain ages. Here are the key milestones from childhood to retirement.

Age calculation seems straightforward, but varying month lengths and leap years introduce complexity. February has 28 days in common years and 29 in leap years. Months range from 28 to 31 days, meaning the number of days in "one month" depends on which month you are counting through.

A leap year occurs every 4 years, except for century years that are not divisible by 400. So 2000 was a leap year, but 1900 was not. If you were born on February 29, your birthday only occurs once every four years on the exact date. In non-leap years, most people celebrate on either February 28 or March 1.

In most legal contexts in the United States, a person's age increases by one year on their birthday. For age verification purposes, the exact time of birth is generally not considered — only the calendar date matters. This calculator follows the same convention, counting whole calendar days.

The Western zodiac divides the year into 12 signs based on the sun's position. The Chinese zodiac follows a 12-year cycle, with each year assigned an animal. Your Chinese zodiac animal is determined by your birth year, though the traditional Chinese calendar starts in late January or February.

If you need to calculate differences in working days rather than calendar days, or want to add a specific number of days to a date, try our date calculator. For college students tracking academic progress, our GPA calculator is a useful companion tool.