Inches to Roman Inches (in to uncia)

1 inch equals 1.032520325 Roman inches (rounded).

1 inch = 1.032520325 Roman inches

How to convert inches to Roman inches

To convert inches to Roman inches, multiply the number of inches by 1.032520325. The factor is rounded to 10 significant digits. To go the other way, multiply Roman inches by 0.968503937 (rounded).

Roman inches = inches × 1.032520325

Example: 10 inches = 10.32520325 Roman inches.

Approximate value. Standards for the Roman inch (uncia) varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

About these units

Inch (in)

US & ImperialCurrent unit

1/12 of a foot. Defined as exactly 25.4 millimeters since 1959, when the US and Commonwealth countries agreed a common international inch.

Latin uncia, meaning one-twelfth, is the root of both inch and ounce, and it passed into Old English as ynce. Roman measurers divided their foot into twelve unciae, and the English inch kept that twelfth. After 1066 an inch was reckoned as three barleycorns, and a 1324 statute attributed to Edward II spelled out the definition as three grains of barley, dry and round, placed end to end lengthwise. For centuries the inch was simply a twelfth of a foot, or a thirty-sixth of a yard, and the US and UK each kept their own copy of the standard yard.

Those copies differed slightly until the 1959 international agreement fixed the yard at exactly 0.9144 meter, which made the inch exactly 25.4 millimeters. The US adopted it in 1959 and the UK ratified it in 1963, effective 1964. Today the inch is still the customary unit in the United States and Canada, and the UK keeps it on road signs. Worldwide it also names display diagonals, wheel rims, tire codes and pipe sizes.

1 inch = 0.0254 meters (exactly).

Sources: Wikipedia: Inch; Wikipedia: Yard; NIST Guide to the SI, Appendix B.8: conversion factors

Roman Inch (uncia) (uncia)

Ancient RomanHistorical unit (no longer in standard use)Approximate value

One twelfth of a Roman foot, about 2.46 cm. Its name, uncia, is the root of the English words 'inch' and 'ounce'.

Twelve of these made up a Roman foot, and that fraction is the whole meaning of the name: uncia is Latin for a twelfth. The same word was applied to weight, where it gave the ounce as a twelfth of the Roman pound. Because the foot is about 296 mm, the uncia works out to roughly 24.6 mm, the value Wikipedia gives, though that article notes the figure lacks a citation. Any difference in the foot carries straight through to its inch.

Latin also had pollex, meaning thumb, as a synonym for the length. Old English borrowed uncia as ynce, and a regular sound change turned it into the modern word inch, which is a cousin of ounce. The English inch kept the idea of a twelfth of a foot but was later fixed by international agreement at exactly 25.4 mm, so it is about 3 percent larger than the Roman original.

1 Roman inch (uncia) = 0.0246 meters (approximately).

Sources: Wikipedia: Roman inch; Wikipedia: Inch; Wikipedia: Ancient Roman units of measurement

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