Square feet and linear feet are two terms of measurement you'll hear when shopping for floor coverings and other construction materials. It's important to understand the difference between them when comparing prices since lumber is typically sold by the linear foot while carpet and plywood are sold by the square foot. It's also helpful to know how to convert between the two using paper and pencil or an online calculator.
Linear Foot vs. Square Foot
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A linear foot is a measure of distance, such as the length or width of a room. It consists of 12 inches, just like a regular foot of measurement. The addition of the term linear simply indicates that the measurement in one direction along a line. A linear foot is a one-dimensional measurement.
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A square foot is a measure of area that is calculated from the length and width of an enclosed space like a room. The area of a square foot in inches is calculated by multiplying 12 inches by 12 inches, which is the same as 12 squared. A square foot is a two-dimensional measurement. To determine the square footage of a room, you multiply the length of the room by the width.
Calculating Linear Feet from Square Feet
If you know the square footage of a room, you may want to find out the number of linear feet along the outside edges, or perimeter. To do this you will need to know either the length or the width of the room since different combinations of length and width can result in the same area. A room that is 12 by 10 feet has 120 square feet, as does a room that is 8 by 15 feet.
If you know the area of a room in square feet and one of the room's dimensions in feet, you can find the other dimension by dividing the area by the known dimension. Say that you know a room has 80 square feet with a length of 8 square feet. You divide 80 by 8 for the result of 10, which is the measurement of the room's width in linear feet. To calculate the perimeter, you add two length measurements and two widths. For an 8 by 10 foot room, the perimeter is (8 x 2) + (10 x 2) or 36 linear feet.
Determine Linear Feet for Flooring
Although it's relatively easy to calculate the length or width of a room when you know the square footage by dividing the square footage by the known dimension, it's a bit more complicated to determine how many linear feet of flooring is needed to cover the floor of a specific-sized room. In this case, the width of the floorboards being used needs to be taken into account.
Since floorboard widths measured in inches, a conversion of the room's square feet to inches is also needed. This is done by multiplying the total square footage by 12. So for a room of 100 square feet where a 5-inch wide floorboard is being used, the number of linear feet needed would be (100 x 12) / 5 or 240 linear feet.
Using an Online Linear Foot Calculator
Many lumber and flooring online retailers include calculators that do the math to determine the number of linear feet of flooring needed for a room. To use a linear foot calculator for wood flooring, you typically type in the final width in inches of floorboard and the square footage of the room. The calculator will provide the number of linear feet needed. When measuring the width of floorboards, use the width of the exposed surface of the board, also known as face width. Do not include edges that are hidden when the floorboards are installed.