Japanese School Grade & Age Calculator
Find the age, current school grade in Japan's April-based system, and entrance/graduation years from a birth date — or run it backwards from a grade to the range of birth dates. Early-birthday rules included.
How Japan's school-year cutoff works
Japanese school years run from April to March, and the grade cutoff is April 2nd: children born from April 2nd through April 1st of the following year belong to the same grade. Counterintuitively, a child born on April 1st joins the grade of those born the previous spring — Japanese law counts a person as one year older on the day before their birthday, so an April 1st child turns six "within" the school year that starts on April 1st. Children born January 1st – April 1st are called hayaumare (early-born) and are the youngest in their grade.
Both directions
Birth date → grade gives the current age, the grade for any school year, and a full timeline of entrance and graduation years from elementary school through university.
Grade → birth dates runs the lookup backwards: pick a school year and a grade, and it returns the April 2 – April 1 window of birth dates that belong to it. Useful when checking a class roster or reading a Japanese school document that states a grade rather than a birth year.
Because of the day-before-birthday rule, every child in a grade has reached the same age by March 31, the last day of the school year: grade number plus six. Both views show that number.
Notes
- Grades assume standard progression (no grade repetition or acceleration).
- University assumes a four-year program.
- "Age today" increments on the birthday itself, the everyday convention. The legal age is reached one day earlier, so the two differ on that single boundary day.
- Enrolment decisions are made by the municipal board of education; deferrals and early entry follow their guidance.