How Long Is an Inch?

An inch equals 1/12 of a foot and 1/36 of a yard in the U.S. customary and imperial measurement systems. It also equals 25.4 millimeters, or 0.0254 meters.

The inch is a commonly used unit of measurement in the United States. There have been Scottish inches, continental inches and Amsterdam inches. The English word "inch" comes form the Latin word "uncia," which means, "one-twelfth part." The word ounce, 1/12 of a troy pound, has the same origin. In other languages, the word inch is similar to, or the same as, the word for "thumb" and often has a similar etymology.