A linear foot is a unit of measurement that is used to describe length. There is no difference between a linear foot and a regular foot except that a linear foot is always measured in a straight line. Arcs and perimeters can still be measured in feet but linear feet would not be used to measure real-world objects that are not in the form of straight lines. This type of measurement is commonly used when referring to the length of a piece of lumber. The foot is not a commonly used measurement anymore, though it is the standard in the United States and is currently being used alongside the metric measurements in the United Kingdom.
The linear foot is an old unit of measure that has been in use in some form for thousands of years. The exact measure of the foot varied from country to country and even from person to person and was not formally standardized across international lines until 1959. At this time it was given the exact metric equivalency of 1 foot to 0.3048 meters that is still in use today. Previously, the length of a foot was standardized to a variety of lengths that were all approximately 0.3 meters within individual nations, going back as far as ancient Greece and Rome. The use of a ruler cut to the length of a foot allowed people to measure this length reliably since the length of an actual human foot varies from person to person.
Lumber yards often use the term linear foot interchangeably with foot to describe the length of a board. The term board foot is also commonly used in lumber measurement and refers to the square footage of a board that is one inch thick. It is also common to use linear feet to describe the amount of shelf space that books or files occupy. Libraries and offices may use this measurement to discuss the quantity of books or files that they have.
Like a regular foot, a linear foot can be divided into 12 equal sections called inches (1 inch = 2.5 cm). The inch is believed to be based on the width of the thumb. Some historical records indicate that the length of a foot was based on this measurement rather than the actual measurement of a person's foot. There are also 3 linear feet in a yard, a unit which is used to measure larger objects or pieces of land.