Lumber sizes are usually given in “nominal” measurements. The nominal measurements are a board’s size before it has been planed smooth (surfaced) on all 4 sides. The actual measurements are the final size. If your project calls for precise measurements, be sure to check your lumber before purchasing.

What does nominal size mean?

Nominal size is the size you see printed on the side of your air filter. It stems from the actual size, which is rounded up to the nearest whole inch.

Why are lumber nominal and actual sizes different?

The “nominal” cross-section dimensions of a piece of lumber, such as 2 X 4 or 1 X 6, are always somewhat larger than the actual, or dressed, dimensions. The reason is that dressed lumber has been surfaced or planed smooth on four sides (called S4S). The nominal measurement is made before the lumber is surfaced.

What is the nominal dimension of a 2×4?

Because a nominal 2×4 board is really 1-1/2 inches by 3-1/2 inches. In fact, 2x4s are never 2x4s these days. A nominal 2×4 board starts out 1.56 in. x 3.58 in.

What is nominal size example?

The measurement used in naming a component, not necessarily its actual size when finished or milled. The size of timber is usually given in nominal size, and the actual size is slightly smaller, for example, a 2×4 actually measures 1 5/8 x 3 5/8 inches.

What is basic size and nominal size?

Basic size – The basic size is the size to which allowances and tolerances are added to get the limits of size. 4. Nominal size – The nominal size is a designation used for general identification. Typically this is a fraction when working in inches.

When did lumber become nominal size?

Early concepts called for rough lumber to be of full nominal size, often in the dry condition. After World War I, the increasing demand for construction lumber led to the first national size standard in 1924. This was revised in 1926, 1928, 1939, and 1953, while still another revision is proposed for adoption in 1964.

Is a 2×6 really 2×6?

2x Board Sizes

2×4 and 2×6 boards lose 1/2 inch in thickness and 1/2 inch in width before leaving the mill. That means a 2 x 4 board is actually 1-1/2 inches by 3-1/2 inches. The larger 2x boards (2×8, 2×10, etc.) lose 3/4 inch in width.

What is nominal thickness?

Nominal thickness is “in name only” used solely for identification. The nominal size may not match any dimension of the product, but within the domain of that product. The nominal size may correspond to a large number of highly standardized dimensions and tolerances.

How do you read a wood size?

The first number (2) refers to the thickness of the board in inches. The second number (4) refers to the width of the board in inches. The third number (8) refers to the length of the board in feet.

What is the difference between nominal and dimensional lumber?

Why are the nominal dimensions of lumber larger than the actual dimensions? The simple answer is the nominal measurements were derived from a board’s size before it has been dried and planed smooth (surfaced) on all 4 sides. The actual measurements are the final dried and surfaced size.

Why isn’t a 2×4 actually 2×4?

Now, most timber is milled and planed to give it a little more of a finished look, and a little more of a consistent size and profile. Because of this extra milling, a 2×4 no longer measures a full 2 inches by four inches. Instead, a 2×4 is really only 1 1/2″ by 3 1/2″.

When did 2x4s stop being 2×4?

Size standards, maximum moisture content, and nomenclature were agreed upon only as recently as 1964. The nominal 2×4 thus became the actual 1½ x 3½, imperceptibly, a fraction of an inch at a time.