Ask a collector how big a sword is and the honest answer is a single measurement: the nagasa (長さ, pronounced “nah-gah-sah”). Nagasa is the length of the blade — and in the Japanese tradition it is not just a number, it is the line that defines what kind of sword you are holding at all.
What Nagasa Measures
Nagasa is measured in a strict way: a straight line from the tip of the point, or kissaki back to the notch where the hardened blade meets the tang, or nakago. It deliberately ignores the handle and ignores the depth of the curve, or sori — it is the pure straight-line span of cutting steel. That single figure is what separates the families of Japanese swords.
Length Defines the Sword
By tradition, a blade of roughly 60 cm (about two shaku) or more is a katana. Drop into the 30 to 60 cm band and the sword becomes a wakizashi, the companion blade. Shorter still, under 30 cm, and you hold a tanto. The same steel, the same edge, or ha, the same forging — only the nagasa changes the name and the role. See where length sits among the parts on our anatomy of the katana.
Choosing the Right Nagasa
For a buyer, nagasa is the most personal spec on the whole sword, because it has to fit your body and your practice. Too long and the blade feels unwieldy and slow on the draw; too short and your cuts lose reach and authority. A rough traditional guide ties blade length to your height and arm span, but practice style matters too. If you are choosing your first sword, our guide to choosing a katana walks you through matching nagasa to your stature, and our beginner katana range is sized for newcomers learning the basics.