cubit

The cubit is an ancient unit of length used in the Near East and the Mediterranean, defined as the distance from the elbow to the tip of the middle finger. The word cubit derives from the Latin cubitus, meaning elbow. Lengths assigned to the cubit varied by culture and era, with approximate values commonly cited between 0.45 and 0.53 meters. Prominent forms include the Egyptian royal cubit and the Hebrew or common cubit.

Cubits were typically subdivided into smaller units to facilitate measurement, such as palms and fingers. Subdivision schemes differed by culture; in ancient Egypt two main forms were used (royal and common), and similar concepts appear in Mesopotamia and other regions. Even where lengths differed, the general principle was a standardized unit that could be reproduced with measuring rods.

In practice, cubits guided construction, land surveying, taxation, and ritual design. Egyptian architecture, including temples and monuments, relied on royal cubit measurements; other civilizations used their own cubit-based systems to lay out buildings, fields, and edicts. Archaeologists determine ancient dimensions by examining inscriptions, artifacts, and cubit rods, then convert to modern units.

Today the cubit is mainly of historical and scholarly interest, used to interpret ancient texts and archaeology. It is easy to confuse with qubit, a modern term in quantum information science referring to a unit of quantum information.