The best katana length is subjective and can vary based on personal preferences, intended use, and the individual's physical characteristics. Traditional katana blades typically range from around 60 centimeters (24 inches) to 80 centimeters (31 inches) in length, with the average falling between 65 and 75 centimeters (26-30 inches).

The ideal katana length depends on factors such as the user's height, arm length, and preferred handling characteristics. Here are a few considerations:

1. Proportions: The katana should be proportionate to the user's body size and arm length. It should feel comfortable and well-balanced when held and swung.
2. Control and Maneuverability: A shorter katana may offer greater control and maneuverability, allowing for quick strikes and changes in direction. This can be beneficial in close-quarters combat or fast-paced fighting styles.
3. Reach and Cutting Power: A longer katana can provide increased reach, allowing for strikes from a greater distance. It can also generate more power and leverage in cutting techniques.
4. Style and Purpose: Different martial arts styles or personal preferences may favor specific katana lengths. Some styles emphasize speed and precision, while others prioritize power and cutting ability.

Ultimately, the best katana length is one that suits the individual's physical attributes, combat style, and preferences. It is recommended to handle and test different katana lengths, seeking guidance from experienced practitioners or instructors to determine the most comfortable and suitable length for your specific needs.