The inch (abbreviation: in or ″) is a unit of length in the (British) imperial and United States customary systems of measurement now formally equal to 1⁄36 yard but usually understood as 1⁄12 of a foot. Inches to cm converter. Easily convert Inches to Centimeters, with formula, conversion chart, auto conversion to common lengths, more. Convert centimeters (cm) to inches. inches to cm, cm to inches calculator. convert inches & centimeters. nursing calculators. Actual size of Inch Ruler. width:12.0Inch (304.8mm). full screen drag it iframe embed. +. Actual size image of Inch Ruler . Inches. Use of the inch can be traced back as far as the 7th century. The first explicit definition we could find of its length was after 1066 when it was defined as . Inches conversion calculators, tables and formulas to automatically convert from other length units. Inch definition is - a unit of length equal to 1/3₆ yard. How to use inch in a sentence. Did You Know? An inch is a measure of length in US units. There are 12 inches in a foot, and 36 inches in a yard. This ruler (not to scale) measures up to 12 inches (or up to 30 .