Just how long is a cubit? It depends on whom you ask. Noah’s cubit was somewhat longer than the Egyptian, Greek and Roman cubit. For Noah, the cubit was the measurement from his elbow to the tip of his middle (longest) finger. This inexact measurement likely caused great problems throughout the world, particularly in Africa, where a cubit could range anywhere from less than 12 inches (for pygmy cultures) to more than 36 inches (for the Watusi).
Most sources agree that a cubit in the Bible was equal to 21.8 inches, an Egyptian cubit was equal to 20.6 inches, a Greek cubit was equal to 18.3 inches, and a Roman cubit was equal to 17.5 inches.
To complicate things, there is another type of cubit. A “short” cubit is the length of the forearm, not including any part of the hand. Scholars believe that this unit was occasionally used in the Bible as well, as in the case of the height of Goliath. Said to be “six cubits and a span” tall, David’s target would have been nearly 11 feet tall using a regular cubit, but a more likely height of 6’ 9” using the “short” cubit. Because humans were shorter during ancient times, a man of that height could have been considered a giant, despite the fact that he would have had difficulty dunking on Patrick Ewing.