It may have originated in Egypt about 3000 bc; it thereafter became ubiquitous in the ancient world. The cubit, generally taken as equal to 18 inches (457 mm), was based on the length of the arm from the elbow to the tip of the middle finger and was considered the equivalent of 6 palms or 2 spans.

How long was the Egyptian cubit?

The earliest attested standard measure is from the Old Kingdom pyramids of Egypt. It was the royal cubit (mahe). The royal cubit was 523 to 525 mm (20.6 to 20.64 inches) in length: and was subdivided into 7 palms of 4 digits each, for a 28-part measure in total.

What is cubits in the Bible?

The cubit is an ancient unit of length based on the distance from the elbow to the middle finger. It's primarily associated with the Sumerians, Egyptians and Israelites. "Cubits" is found in the Bible re: Noah's Ark, Ark of the Covenant, Tabernacle, Solomon's Temple.