Each official professional sumo tournament lasts 15 days. Japan’s six annual honbasho, or grand tournaments, run on consecutive days, with wrestlers competing according to their rank and division.
Top-division wrestlers normally have one bout per day during the tournament. A wrestler’s record after 15 days determines whether they achieve a winning record, called kachi-koshi, or a losing record, called make-koshi. For most wrestlers, eight wins are needed for a winning record in the 15-day top-division competition.
The 15-day format is a modern feature of professional sumo rather than a description of every sumo event in history. Lower-ranked wrestlers may compete on fewer days, and exhibition events follow different schedules. The six major tournaments are held in Tokyo in January, May and September, while Osaka, Nagoya and Fukuoka host the other three.