Calculator for adding, subtracting, multiplying and dividing feet and inches using whole numbers, mixed numbers and fractions. Construction related calculator to solve problems with feet and inches calculations. Free online calculator for adding, subtracting, multiplying and dividing mixed numbers and fractions.. Millimeters. The millimetre is a unit of length in the metric system, equivalent to one thousandth of a metre (the SI base unit of length). One meter was defined in 1983 by the 17th conference of weights and measures as “the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second” and the millimetre by definition is derived as being 1/1000th of . There are 36 inches in a yard and 12 inches in a foot. The inch is usually the universal unit of measurement in the United States, and is widely used in the United Kingdom, and Canada, despite the introduction of metric to the latter two in the 1960s and 1970s, respectively.. An inch is a unit of Length or Distance in both US Customary Units as well as the Imperial System. The symbol for inch is in or ". There are 0.39370079 inches in a centimeter. What is a centimeter (cm)? A centimeter is a unit of Length or Distance in the Metric System. The symbol for centimeter is cm. There are 2.54 centimeters in an inch.. Linear inches is a term invented by the airline industry to measure baggage. The size of an item in linear inches is the sum of the length plus the width plus the height of the item. A 20-by-20-by-5-inch suitcase, a 1-by-11-by-4-inch painting and a 1-by-1-by-43-inch fishing rod are all the same size in terms of linear inches.. The international standard symbol for a foot is "ft" (see ISO 31-1, Annex A). In some cases, the foot is denoted by a prime, which is often marked by an apostrophe, and the inch by a double prime; for example, 2 feet 4 inches is sometimes denoted as 2′−4″, 2′ 4″ or 2′4″..