A kodachi is a traditional Japanese short sword, often considered a companion to the longer katana. The blade length of a kodachi typically ranges between 18 to 24 inches (45 to 61 centimeters).

The exact length of a kodachi can vary based on the specific design, historical period, and individual swordsmith preferences. The kodachi is shorter than a standard katana but longer than a tanto (a shorter dagger-like blade).

The kodachi was primarily used in close-quarter combat or as a backup weapon. It offered a shorter reach compared to the katana but provided greater maneuverability in tight spaces or indoor environments.

It's important to note that the measurements provided are approximate and can vary between individual kodachi swords due to variations in historical examples, regional preferences, and personal tastes of sword owners or collectors.

In summary, the blade length of a kodachi generally falls within the range of 18 to 24 inches (45 to 61 centimeters), making it shorter than a katana but longer than a tanto.