Linear footage is the same as length; if a man is 6 feet tall, then he has 6 linear feet. Linear means "straight line." The straight distance from point A to point B is the linear distance between those two points.
Calculating linear footage doesn't take into account the width of the object. For example, if lumber is sold by linear foot, then two pieces of lumber both 10 feet long are the same price even though one piece might be 1 foot wide and the other piece is 2 feet wide.
Sometimes a measurement of linear feet is applicable for a purchase, such as floor molding or trim that has per linear foot pricing. To calculate the amount needed, the homeowner measures the length of each wall. Or if the homeowner knows the room is 10 feet wide and 15 feet long, he would just add the two walls of 10 feet and the two walls of 15 feet to equal a total linear footage of 50 linear feet.
Often a homeowner needs to know square footage rather than linear footage. Most floor covering retailers sell their products by the square foot because carpet and flooring cover an area. Square feet are calculated using the formula for area: width times height. A room that is 10 feet wide and 15 feet long has an area of 150 square feet.
Linear measurements also measure mileage. The distance between two places expressed in linear mileage is the length of a straight line between those places, not the actual driving or flying mileage.