Convert from inch [international, U.S.] to cubit [Roman]

Unit Definition (inch [international, U.S.])
The inch is a traditional measurement of distance equal to 1/12 of a foot, or exactly 2.54 centimeters. The Old English word "ynce" is derived from the Latin uncia, meaning a 1/12 part. It follows that "inch" and "ounce" actually have the same origin. The inch was originally defined in England in two ways: as the length of three barleycorns laid end to end, or as the width of a man's thumb at the base of the nail. The barleycorn definition is peculiarly English, but the thumb-width definition is generic. In many european languages the word for inch actually also means thumb: examples include the Dutch duim, Swedish tum, French pouce, and Spanish pulgada. In the history of English units the inch seems to come before the foot, as after the Norman conquest of 1066, the foot was defined as 12 inches, rather than the inch being defined as 1/12 foot.

Unit Definition (cubit [Roman])
The cubit is a historic unit of distance frequently mentioned in the Bible. The word comes from the Latin cubitum, "elbow," because the unit represents the length of a man's forearm from his elbow to the tip of his outstretched middle finger. This distance tends to be about 18 inches or roughly 45 centimeters. In ancient times, the cubit was usually defined to equal 24 digits or 6 palms. The Egyptian royal or "long" cubit, however, was equal to 28 digits or 7 palms. In the English system, the digit is conventionally identified as 3/4 inch; this makes the ordinary cubit exactly 18 inches (45.72 centimeters). The Roman cubit was shorter, about 44.4 centimeters (17.5 inches). The ordinary Egyptian cubit was just under 45 centimeters, and most authorities estimate the royal cubit at about 52.35 centimeters (20.61 inches).