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What Is The Difference Between Actual And Nominal Lumber dimensions?

October 19, 2018Olen Murriel

The actual and nominal dimensions of lumber are not similar; The may result to confusion due to the anticipation that the nominal dimensions of a piece of timber or any other lumber product for example a 2 x 4 piece of timber represent its actual dimensions. This is not the case since the lumber measurement displayed at the store is not equal to the actual dimensions that you will get after measuring the lumber.

Due to this difference in sizes, beginners in woodworking are faced with a difficult challenge when they need to purchase lumber products for their projects since the dimensions by which the wood are displayed at the lumber store are not equal to the actual dimensions of the wood when it is measured. As a result of this, one will find that a piece of dimensional lumber whose nominal dimensions 2 x 4 inches will have it actual dimensions as 1.5 x 3.5 inches.

In addition to this, Hardwoods and softwood are measured using different sizing methods. The sizing method used to measure hardwood lumber uses board foot to determine its dimensions. The information below will help you to understand the difference between actual and nominal Lumber dimensions hence helping you to avoid the confusion that may arise from the topic.

The Difference Between Actual And Nominal Measurements of Dimensional Lumber.

Softwoods for example pine which intended for use in a wide range of carpentry projects is commonly known as dimensional lumber In reality, the nominal dimensions of softwood lumber are not equivalent to its actual dimensions; this is because dimensional lumber is cut with it nominal dimensions equal to the actual dimensions from a wet tree. After going through the necessary processing, the lumber dries thus making it difficult to maintain the standard measurements. In addition, the resulting lumber (dry) is polished causing its size to decrease further.

In the current lumber industry, it is not common to find softwood boards that have equal nominal and actual dimensions. For example, a piece of timber whose nominal dimensions is 2 x 4 inches may even measure less than that initially before processing. However with the advanced technology used during processing; the piece of lumber will still have a standard size of about 1.5 x 3.5 inches.

 

General dimensions for softwood lumber

Nominal Lumber Size

  • 1 x 2 inches
  • 1 x 3 inches
  • 1 x 4 inches
  • 1 x 5 inches
  • 1 x 6 inches
  • 1 x 8 inches
  • 1 x 10 inches
  • 1 x 12 inches
  • 2 x 2 inches
  • 2 x 3 inches
  • 2 x 4 inches
  • 2 x 6 inches
  • 2 x 8 inches
  • 2 x 10 inches
  • 2 x 12 inches
  • 4 x 4 inches
  • 4 x 6 inches
  • 6 x 6 inches

Actual Lumber Sizes

  • 0.75 x 1.5 inches or (19 x 38 mm)
  • 0.75 x 2.5 inches or (19 x 64 mm)
  • 0.75 x 3.5 inches or (19 x 89 mm)
  • 0.75 x 4.5 inches or (19 x 114 mm)
  • 0.75 x 5 .5 inches or (19 x 140 mm)
  • 0.75 x 7.025 inches or (19 x 184 mm)
  • 0.75 x 9.025 inches or (19 x 235 mm)
  • 0.750 11.025 inches or (19 x 286 mm)
  • 1.5 x 1.5 inches or (38 x 38 mm)
  • 1.5 x 2 .5 inches or (38 x 64 mm)
  • 1.5 x 3 .5 inches or (38 x 89 mm)
  • 1.5 x 5 inches or (38 x 140 mm)
  • 1.5 x 7.025 inches or (38 x 184 mm)
  • 1.5 x 9.025 inches or (38 x 235 mm)
  • 1.5 x 11.025 inches or (38 x 286 mm)
  • 3.5 x 3.5 inches or (89 x 89 mm)
  • 3.5 x 5.5 inches or (89 x 140 mm)
  • 5.5 x 5.5 inches or (140 x 140 mm)

Note that the width of the wood experiences a greater reduction in size as compared to the length of the wood.

Sizing Of Hardwood Lumber

Hardwoods are measured using different sizing methods that use board foot to measure the dimensions. Hardwoods for example mahogany, birch, maple, and oak is intended for use in advanced carpentry projects such as making high-quality furnishings and cupboards. In addition, the sizing of hardwood lumber is also done according to its nature for instances is it surfaced on both faces (S2S) or on a single face (S1S)?

Nominal Thickness Of Hardwood Lumber

  • 0.5 inches (1/2)
  • 0.625 inches (5/8)
  • 0.75 inches (3/4)
  • 1 inch (4/4)
  • 1.25 inches (5/4)
  • 1.5 inches (6/4)
  • 2 inches (8/4)
  • 3 inches (12/4)
  • 4 in (16/4)

Hardwood Lumber Surfaced On One Side (S1S)

  • 0.375 inch or (9 1/2 mm)
  • 0.5 inch or (13 mm)
  • 0.625 inch or (16 mm)
  • 0.875 inch or (22 mm)
  • 1.125 inches or (29 mm)
  • 1.375 inches or (35 mm)
  • 1.8125 inches or (46 mm)
  • 2.8125 inches or (71 mm)
  • 3.8125 inches or (97 mm)

Hardwood Lumber Surfaced On Two Sides (S2S)

  • 0.31 inches or (7.9 mm)
  • 0.44 inches or (11 mm)
  • 9/16 inches or (14 mm)
  • 0.8125 inches or (21 mm)
  • 1.17 inches or (27 mm)
  • 1.31 inches or (33 mm)
  • 1.75 inches or (44 mm)
  • 2.75 inches or (70 mm)
  • 3.75 inches or (95mm)

 

Unlike softwoods, hardwoods are not measured using standard dimensional methods. Hardwoods are measured using the board foot method this means that a 1-inch thick board that measures 12 inches in both its length and width contains 144 cubic inches of hardwood which is equivalent to one board foot.

Also, hardwood may be traded in pieces measuring 025 inches in thickness : these pieces are called quarters. This implies that apiece of hardwood board with 5/4 inches nominal thickness is about 125 inches thick. Thus, for a project that requires a board with a 1-inch thickness; one will be required to buy a board whose thickness is 5/4 inches and split it to the desired thickness.

Plywood

Plywood is commonly traded in sheets that measure about 4 x 8 feet. Though they are commonly available in sheets measuring 0.75 and 0.5 inches in nominal thickness; their actual and nominal sizes may not match. As a result, a sheet of plywood with 0.5-inch nominal thickness has an actual thickness 01 046 inches, whereas a sheet measuring 0.75 inches has an actual thickness 01 072 inches.

In addition, plywood faces are categorized into grades for instance; grade A, B, C, and D. A sheet of plywood whose grade is AA has both faces sanded to attain a smooth furniture-grade finish.

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