So, 30" would make it a Katana wouldn't it? This stolen from Wiki, if you can believe them.

The length of the Katana blade varied considerably during the course of its history. In the late 14th and early 15th centuries, katana blades tended to have lengths between 70 and 73 cm (27½ and 28½ in). During the early 16th century, the average length approached closer to 60 cm (23½ in).