The length of an iaito, a practice sword used in iaido (the Japanese martial art of drawing and striking with the sword), can vary depending on the individual practitioner's height, arm length, and personal preferences. However, there are some general guidelines to consider when determining the appropriate length for an iaito:

1. Blade Length: The blade length of an iaito is typically similar to that of a standard katana. It generally ranges from approximately 25 inches (64 cm) to 30 inches (76 cm). The blade length should be chosen based on factors such as the practitioner's height, arm length, and the desired balance and handling characteristics.
2. Total Length: The total length of an iaito, including the hilt (tsuka), can range from around 39 inches (99 cm) to 43 inches (109 cm) on average. This measurement can be influenced by personal preferences and the specific design of the iaito.

It's important to note that the length of an iaito should be selected to suit the individual practitioner's physique, arm length, and their ability to perform iaido techniques comfortably and effectively. The iaito's length should allow for smooth and controlled drawing, striking, and sheathing movements without excessive strain or imbalance.

To determine the most suitable length for an iaito, it is advisable to consult with experienced iaido instructors, knowledgeable practitioners, or trusted sword suppliers. They can provide guidance based on their expertise and help ensure that the iaito's length is appropriate for the practitioner's needs and physical characteristics.