1×8  lumber actual size

The actual size of 1 x 8  lumber is around 3/4″ x 7 1/4 inches (19 x 184 mm). This is a smaller size than the nominal size. Despite the inaccuracy in the size, it is still referred to as 1-by-8 lumber in hardware stores due to the standard of measurement. And According to technical terms, 1×8 is the correct measurement, since the dimensions were correct before the lumber was treated and smoothed.

The length of a 1×8  board remains the same regardless of whether it is nominal or actual. For example, if the nominal length of 1×8  is 8 feet, the actual length will be 8 feet. Similarly, if the nominal length is 8 feet then the actual length would be 8 feet, and so a 12 feet length board will actually be 12 feet long, the same as the nominal length.

However, it’s better to do some quick measurements to find out the exact length.

1×8  lumber dimensions (Actual vs Nominal)

1×8  lumberNominal size in inches Actual size in inches
Width1 Width3/4
Height 8 length7 1/4 inches 
1×8  LumberNominal size in mmActual size in mm
Height 152.4184 

Why is the actual size of a 1 x 8  lumber smaller than its nominal size?

The size of natural lumber is larger because of its moisture content, which shrinks after treatment. Home Depot and local hardware stores sell lumber with smoothed and planned edges- that are smoothened. In a lumberyard or hardware store, lumber is sold by its nominal size, referring to dimensions before treating, planning, and smoothing, not by its actual true size.

Green or fresh timber has a rough surface. To make the surface smoother, timber goes through a planer, on the sides to create a uniform thickness. As a result of planning through each side of the timber, the thickness of the timber shrinks as thin layers are sliced away, leading to a thin edge. Due to this, timbers with 4-sided smooth surfaces generally lose thickness and width, so their actual size is reduced.

Typically, a plank is measured as it is in its original shape, but the lumber we purchase has been smoothened during the manufacturing process. This process results in the board shrinking.

Different sizes of lumbers their actual size

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