The word cubit (singular) occurs over 30 times in the Scriptures, and cubits (plural) over 180 times. What is a cubit and what is the length of one cubit?
The English word cubit comes from the Latin word cubitum (“the elbow, the distance from the elbow to the finger-tips”). A cubit is the mother of the arm, i.e., the fore-part of the arm; cubitus, ulna, the fore-arm.
In measurement, a cubit is the length of the arm from the elbow to the extremity of the middle finger.
Several “official” cubits existed in the ancient Middle East, ranging from about 18 to 22 inches. Lengths differed depending on the culture (e.g., Hebrew, Babylonian) and whether it was a long, short, or royal cubit.
The Egyptian royal cubit measured 20.62 inches and was subdivided in an extraordinarily complicated way. The Babylonian cubit measured about 20.9 inches. The Hebrews had two cubit measurements: short (est. 17.5 inches) and long (est. 20.4 inches). The common Hebrew cubit was six palms; a larger cubit of seven palms is mentioned in Ezekiel 40:5; 43:13.
Due to various things, including the fact that everyone’s cubit size is different, the “exact length” of the ancient Hebrew or Jewish cubit is unknown. Some fix the Hebrew cubit at twenty inches and a half, and others at eighteen. The latter seems to be the preferred and most widely used length among researchers, and it is the cubit length used by Cory Trout Ministries.
References:
“Cubit, n.s.” A Dictionary of the English Language, by Samuel Johnson. 1755.
Webster, Noah, and Rosalie J. Slater. “Cubit.” Noah Webster’s First Edition of an American Dictionary of the English Language, Foundation for American Christian Education, 2009.
“Cubit.” The Compact Edition of the Oxford English Dictionary: Complete Text Reproduced Micrographically, I A-O, Oxford University Press, 1971, p. 619.
“Measurement system.” Edited by Zupko, Ronald and Chisholm, Lawrence James, Encyclopædia Britannica, Encyclopædia Britannica, Inc., 19 Nov. 2018, https://www.britannica.com/science/measurement-system.