The ideal length for a katana can vary depending on personal preference, intended use, and the physical attributes of the wielder. Traditionally, a standard katana has a blade length of around 60 to 75 centimeters (24 to 29 inches), with an average total length of approximately 100 to 105 centimeters (39 to 41 inches) including the handle.

However, it's important to note that the optimal length for a katana is subjective and can be influenced by factors such as the wielder's height, arm length, and individual fighting style or techniques. Some practitioners may prefer slightly shorter or longer blades based on their specific needs and preferences.

Shorter blades may provide increased maneuverability and quicker handling, making them suitable for close-quarters combat or indoor use. Longer blades, on the other hand, can offer better reach and leverage for powerful strikes or wider sweeping motions.

If you are considering obtaining a katana for martial arts training or practice, it is advisable to consult with an experienced instructor or expert in Japanese swordsmanship. They can provide guidance and recommend an appropriate length based on your physique, skill level, and specific objectives.

Ultimately, the best length for a katana is a subjective choice that should take into account individual preferences, intended use, and the guidance of a knowledgeable instructor or expert.