Board Foot - Linear Feet - Quarters

Shop Measurements

Introduction: Last week I had a student making a project in the wood shop. He was thoroughly confused about wood measurements so we had a little lesson on the subject.

If you are trying to figure out what a board foot or how many board feet are required to build a project or if you are trying to determine the difference between linear feet and board feet, an explanation is offered below. In addition, shop projects material thickness is referred to in quarters: three quarter, four quarter, five quarter, etc.  Nearly all shop project and construction project plans talk to these three measurements when determining material needs. So let us help you figure it all out.

Board feet:

A board foot refers to a specific volume of lumber. That is to say the width times the length times the depth equals the number of board feet. A one foot (12 inches) long by one foot (12 inches) wide by one inch thick equates to one cubic foot of lumber or one board foot of lumber. Board feet refers to the thickness and width of lumber, before drying and plaining. It is lumber in the rough. Most shop and construction lumber is planed at a mill yard before it is delivered to a retail sales store although rough lumber can be purchased at specialty lumber sales stores.

To determine the number of board feet in a project such as a deck we simply measure the width and depth and multiply them together then multiply the product times the thickness of the material.  A 12 X 14 foot deck made with 3/4 thickness decking would equate to 12 X 14 X 3/4 = 126 board feet of material. Normally we don’t refer to lumber in terms board feet as the thickness is taken for granted. We refer to the quantity of decking required in square feet. In this example it would be 168 sq. ft.

Linear feet:

One linier foot is simply a one foot length of lumber regardless of the width or thickness.  The term is often referred to as the international foot although in other countries it may be expressed in meters.

Quarters:

All wood thickness is referred to in quarters or quarter inches, which is the thickness of the material before milling. A finished planed 3/4 inch thickness of wood is referred to as four quarters (4/4). A one inch thickness would be expressed as five quarters (5/4) although it only measures one inch thick. Shop project hardwoods can be purchased up to eight quarters (8/4) which measures 1 and 3/4 in thickness. All thickness measurements in wood are referred to in its rough form that is before milling.  A rough finish 4/4 would actually be one inch thick.

There you have it, the mystery of shop and project lumber measurement is solved.