tachi vs katana length
Generally speaking, the tachi is longer, with a blade length of more than 80 cm, and the lengths are divided into odachi (over 150 cm) and kodachi (under 80 cm), while the blades of the uchikatana are basically between 70 and 80 cm in length, and the sori of the tachi is usually larger in comparison to the two. Generally speaking, the tachi is longer, with a blade length of more than 80 cm, and the length of the blade is differentiated between odachi (over 150 cm) and kodachi (under 80 cm), while the blade length of the uchikatana is basically between 70-80 cm, and the sori（radian） of the tachi is usually larger. of the tachi is usually larger in comparison.
The difference between Tachi and Katana
The two were used in different times and situations, with tachi being used mainly from the late Heian Period (12th century) to the early Muromachi Period, and katana being used later than tachi, from about the middle of the Muromachi Period to the end of the Edo Period. Therefore, it can be said that katana is the successor of tachi. In the Heian period, the main form of warfare was horseback fighting, and the tachi was longer, with a higher siri (curvature) and an upturned handle, so the tachi was more suitable for use on horseback. From the Muromachi period to the Edo period, the main form of warfare and combat was on the ground, and the katana had a smaller curvature, slightly less cutting ability, and was not long enough, so the katana was mainly used when a person was standing on the ground.
The difference in fighting methods also leads to the difference in the way the tachi and katana are carried. The tachi is carried with the blade pointing down and is more cumbersome, so it must be drawn and prepared in advance when fighting on horseback. The katana is carried with the blade up and is more flexible, making it easier to quickly draw the blade for attack and defense.
It can also be distinguished by its saya, a cavalryman's sword. An important feature of the tachi is that the scabbard is fitted with two ashikanamono, which are mounted with suspension fittings and are easy to carry on horseback, whereas the saya of the katana usually does not have an ashikanamono, and after the Showa era many of the newer tachi models became so close to the katana that they are sometimes difficult to distinguish from the katana simply by looking at the blade.
These are just some of the differences between tachi and katana in general, but there are some exceptions, such as the "handachi" which combines the characteristics of the two, a type of sword that was used during the transition from tachi to katana, and which also has the kurikata of katana in its tosogu, but is worn with the blade facing downwards like a tachi. The tosogu of the handachi also has the kurikata of the katana, but is worn with the blade facing downward like the tachi. There are also swords that were originally tachi, but were later shortened nakago and converted for use as katana, and both Oda Nobunaga and Toyotomi Hideyoshi were converted in this way.