A linear foot, otherwise known as a lineal foot, is equivalent to any one-foot length of a long object, and there is no difference in length between one linear foot and one foot. Particular industries, such as construction and archiving, use the term linear foot to avoid confusion with the square foot or cubic foot.

The construction industry uses linear feet to distinguish it between square feet, cubic feet or others. For instance, purchasing ceramic tiles requires using square feet. However, buying a tile border uses linear feet since the width of the border is irrelevant. Another example is the term board-foot, which is commonly used in the lumber industry. This is equivalent to the volume of a 1-foot length of board that is 1 foot wide and 1 inch thick. The thickness and width are both important factors for manufacturers and purchasers of wood.

The archiving industry also often uses linear feet to report the shelf space needed to store documents. Most letter size documents are slightly less than 1 linear foot. The term linear feet is used to distinguish between cubic feet, which the industry also uses. Cubic feet measures the volume of shelf space needed.

The word linear is not unique in describing feet. Other terms, including linear meter and linear yard, are used similarly to describe meter and yard lengths.

Linear feet is calculated by adding the lengths of points connected by straight lines. For example, the perimeter around a house can be measured in linear feet. Square feet measures area, and linear feet measures length.

Two areas that measure the same square feet can have different perimeters, hence differing values for linear feet, if they’re shaped differently. For example, a rectangle that measures 8 feet long and 2 feet wide has an area of 16 square feet (length x width) and a perimeter of 20 linear feet (2 x (length + width), while a square that measures 4 feet by 4 feet has the same area but a perimeter of 16 linear feet.