Calculate the full age, kazoe (traditional) age, days lived, and days until the next birthday from a date of birth
The full age counts the day of birth as 0 years old and adds 1 year at each birthday. This full age is used for official age in Japan. This tool calculates it by checking whether the birthday has already occurred as of the reference date.
Kazoe age counts the moment of birth as 1 year old and adds 1 year at each New Year's Day. As a result, for the same person it is 1 to 2 years larger than the full age. Because it is used for unlucky-year customs and some traditional events, it is shown alongside as a reference value.
By changing the reference date, you can calculate the age as of that day. This is useful for enrollment or start dates, or for confirming things like "how old as of a given year, month, and day" on documents. By default the reference date is today.
Subtract the birth year from the reference-date year, then subtract 1 if the birthday has not yet occurred. For example, someone born on August 15, 2000 counted as of July 21, 2026 is 25 years old, because the birthday has not yet passed. This full age is the standard way of counting age in Japan.
Kazoe age counts a person as 1 year old at birth and adds 1 more year at each New Year's Day (January 1). It is sometimes used for Shichi-Go-San, unlucky-year customs, and similar traditions. In addition to the full age, this tool also shows the kazoe age for reference.
No. All age and days-lived calculations run entirely within your browser. The date of birth you enter is never sent to or stored on any server.