Age Calculator — Your exact age from your date of birth, plus days lived and days to your next birthday
Enter a date of birth to get the exact age in years, months and days, the total days, weeks and months since birth, and a countdown to the next birthday. Includes a note on how Japan counts age for school-year cutoffs.
Enter a date of birth to see today's age and how many days that is.
Age Calculator: tips and things to know
- Visit on your birthday and the tool wishes you a happy one.
- The days-since-birth figure lets you spot milestones such as your 10,000th day.
- Under Japanese law you legally become a year older at the end of the day before your birthday, which is why a child born on April 1 joins the school year above a child born on April 2.
How to use the Age Calculator
Enter your date of birth
Choose the year, month and day.
Read your age
Your age in full years and the exact years, months and days appear.
See the details
Days, weeks and months since birth, and the countdown to your next birthday.
Age and the Japanese school year
The Japanese school year starts on April 1, and a child enters elementary school in the April after turning six. Because the law counts a person as a year older at the end of the day before their birthday, a child born on April 1 has already turned six on March 31 and joins the year above a child born on April 2. This is a well-known quirk that matters when enrolling children born in late March or on April 1.
Official forms in Japan ask for age in full years (man nenrei, 満年齢), which is what this tool shows. The traditional counting method (kazoe-doshi), where everyone is one at birth and gains a year each New Year, survives only in shrine ceremonies and yakudoshi charts.
Age Calculator FAQ
What is the difference between full age and counted age?
Full age (man nenrei) counts from zero at birth and adds one on each birthday; it is what forms and documents use. Counted age (kazoe-doshi) starts at one and adds one every January 1; it survives only in traditional contexts.
What does "a year older the day before your birthday" mean?
Japan's age-calculation law adds a year at the end of the day before the birthday. In practice it only matters for school-year cutoffs: a child born on April 1 belongs to the previous school year.
What is the days-since-birth figure for?
Milestones such as the 1,000th, 10,000th or 20,000th day are popular to celebrate or post about.