Board Feet Vs. Square Feet in Lumber

Running or Lineal Feet

• Measure the length of the area to be covered when calculating material needs for projects such as fascia or molding, where one continuous material is installed in a line. The material in this case is typically a specific molding product, with consistent width and thickness, or a specific size of dimensional lumber, for example a 1-by-4. A straight line measurement from end to end is typically adequate to estimate the amount of material needed. Always add 15 to 20 percent for miscuts and unusable lumber.

Measuring Width

• On more complex projects, such as decking and flooring, the dimension of width becomes a factor as well. When measuring a rectangular, or square area, take measurements in both directions from both corners and across the center of the area. Use the largest of the three measurements when making calculations to ensure that the proper amount of material is purchased. Always add a 15 percent to 20 percent cushion for mistakes or miscalculations.

Square Feet

• Calculate square feet by multiplying width times length. Use the measuring techniques in the Measuring Width section to determine how wide and long the area you need to cover is. Always estimate high. Multiply these two numbers together to calculate the square footage of the area. Use this surface measurement to order materials such as sheet goods, including plywood and paneling, or dimensional lumber such as decking.

Board Feet

• A board foot is equal to one square foot, at a thickness of 1 inch. Use this dimension when ordering hardwood quantities when the project requires cutting and machining, like furniture building. To calculate the board footage of a particular board, measure the width and length and multiply them to get the square footage. Divide square inches by 144 to get the number of square feet. Multiply this by the nominal thickness of your board to find board feet. (Count 3/4 inch thickness as 1 inch and 1 1/2-inches as two, and so on)