Asked by: Adair Tembrockhaus
asked in category: General Last Updated: 9th January, 2020

Why is lumber measured in quarters?

Rough sawn lumber comes in "true" thicknesses as reflected by the "quarters" size. Lumber sized according to "Quarters" reflects the number of quarters of an inch thick the lumber is. To figure the thickness of a board referenced in "quarters" sizes, simply divide the second number (4) into the first number.

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In this way, why is wood measured in quarters?

Rob Johnstone: The “quarter system” is a metric for roughsawn lumber. It simply refers to how many 1/4-inches thick the rough stock is. For example, 4/4 (read out loud as four-quarters) is 1-in. thick in the rough.

One may also ask, is a 4x4 really 4 inches? Believe it or not, there actually is some rhyme and reason for why the actual measurements of dimensional lumber don't match their names.

Actual Dimensions and Nominal Dimensions.

Nominal Measurement Actual (inches) Actual (mm)
2 x 12 1-1/2 x 11-1/4 38 x 286
4 x 4 3-1/2 x 3-1/2 89 x 89
4 x 6 3-1/2 x 5-1/2 89 x 140

One may also ask, why is a 2x4 not 2 inches by 4 inches?

"Dimensional" lumber is the general name for framing lumber. 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 2x4 no longer measures a full 2 inches by four inches.

What size is 4/4 lumber?

Also in North America, hardwood lumber is commonly sold in a "quarter" system, when referring to thickness; 4/4 (four quarter) refers to a 1-inch-thick (25 mm) board, 8/4 (eight quarter) is a 2-inch-thick (51 mm) board, etc.

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