Types of Japanese Swords

How length defines the class

Japanese swords are sorted first by blade length, and length is stated in traditional units. One shaku (尺) is about 30.3 cm. It divides into ten sun (寸) of about 3.03 cm, and each sun into ten bu (分). The measured length of the blade is the nagasa, taken as a straight line from the tip (kissaki) to the notch at the base of the blade (the mune-machi), not following the curve.

On that scale the modern classification used for registered swords is simple at the boundaries. A blade of 2 shaku or more (about 60.6 cm and up) is a long sword, the daito or katana class. A blade of 1 to 2 shaku (about 30 to 60 cm) is a wakizashi, the short sword (shoto). A blade under 1 shaku (under about 30.3 cm) is a tanto. These cutoffs are the historically and legally used dividing lines in Japan; the descriptive names above them (tachi, uchigatana, odachi and so on) describe how a blade was mounted and worn, and those categories overlap in length. A tachi and a katana, for example, both sit in the 2 shaku and over range, so length alone will not tell them apart.

A useful way to read the scale chart above is to hold two ideas at once. The length class (tanto, wakizashi, daito) is a strict measurement in shaku. The type name (tachi, katana, uchigatana, odachi, ko-dachi) layers era and mounting on top of that measurement. A ko-dachi, for instance, is a short blade under 2 shaku that would fall in the wakizashi length band, yet it is named for being a short tachi because it is mounted and worn in tachi style, edge-down. The same physical length can therefore carry a different name depending on how the sword was meant to be worn.

Tachi versus katana: the same length, worn the opposite way

The clearest source of confusion is the tachi and the katana, because a long tachi and a katana can share the same blade length. The difference is how the sword is worn, and it is not a small detail. A tachi (太刀) is worn slung from the belt with the cutting edge facing down. A katana (刀) is worn thrust through the sash with the cutting edge facing up. Tachi generally show a deeper curvature and belong to an earlier era; the edge-up wearing style came later with the uchigatana and the katana.

Because the wearing orientation is flipped, the smith's signature (mei) is cut on opposite faces of the tang. A mei is inscribed on the side of the tang that faces outward when the sword is worn correctly. On a tachi that is the face pointing away from the body when worn edge-down; on a katana it is the face pointing away when worn edge-up. Museums and appraisers use this: hold a blade as a tachi, edge-down, and if the signature reads right way up it was signed as a tachi, while a katana signature will appear upside down in that position.

How the sword changed over time

The classes above are not just parallel options; several of them are stages in a single line of development. The tachi was the mounted warrior's sword of the Heian and Kamakura periods, long and deeply curved and worn edge-down to be drawn across the body on horseback. As fighting shifted toward foot soldiers in the Muromachi period (1336 to 1573), the uchigatana came into its own: worn edge-up through the belt, it could be drawn and cut in a single motion, which suited close infantry combat. The katana as we name it developed out of the uchigatana during that same era. This is why uchigatana and katana are so often treated as the same weapon in Japanese usage, while writers outside Japan tend to separate them as earlier and later stages of one design.

The very large odachi belongs mostly to the same warring-states stretch of history, carried by some foot soldiers and used partly for display of skill and status. Its length made it impractical to draw from the waist, so it was slung across the back or handed to the wielder by an attendant. As the country entered the long peace of the Edo period, the practical need for battlefield swords fell away, and the daisho pairing (below) became more a social institution than a fighting kit.

The daisho pairing

The daisho (大小, literally big-small) is the matched pair of a long sword and a short sword worn together, in practice a katana with a wakizashi. During the Edo period (1603 to 1868) the right to wear the daisho in public was legally reserved to the samurai class, which made the pair a marker of rank as much as a set of weapons. A true daisho with both blades by the same smith is rare; many surviving pairs are matched by their mountings (koshirae) rather than by a single maker.

Polearms and the straight sword

The naginata (薙刀) and the yari (槍) are made as nihonto, meaning their blades are forged by the same traditional methods as a sword and are registered and appraised alongside swords. They are, however, polearms rather than swords: a curved blade on a long shaft in the case of the naginata, and a straight thrusting head on an even longer shaft in the case of the yari. We include them because you will meet them in any serious discussion of nihonto, but the distinction matters.

The tsurugi or ken (剣) is different again. It is straight and double-edged, an older form that largely predates the curved single-edged sword in Japan. By the classical sword period it survived mainly as a ceremonial and religious object rather than a fighting blade, which is why it turns up in Buddhist and Shinto imagery more than on the battlefield.

Comparison at a glance