Relative sizes:

tanto (knife): 11 to 15 inches

tachi: 30 inches and over

katana: 26-30 inches

wakizashi: 16 to 23 inches


Note: Kenshin's sword is a Sakaba, which is basically a reversed Katana, but fighting with it is more difficult than with a Katana because the sword is duller on the edge that goes forward, therefore slower. The aerodynamics of a Sakaba are different than that of a Katana.