How to calculate board feet          

Hardwood lumber used for making cabinetry and furniture is sold on the per board foot measurement. 
This is a measurement that is constant through all thickneses of lumber. Measurement "A" would be the 
thickness in inches, measurement "B" would be the width in inches, and measurement "C" the length in feet.

The formula for calculating  the board feet of lumber would be 

                                                                                 A X B X C
                                                                                       12 

For example, if the piece of lumber was  3 in. thick (A), 8 in. wide (B), and 5 feet long (C), the board feet 
would be 

                                                                   3 X 8 X 5 / 12 = 10 board feet 

This formula is generally used to calculate the board foot quantity of rough lumber. Lumber is initially 
in the rough state. This means that it has been sawn with a large dimensioning machine such as a 
bandsaw, directly from the log, and has not yet been planed or smoothed. This rough lumber will be 
planed to 25/32 in. thick from a rough blank of 1 in. thick when purchased. 

                                                                         
                                                                       Types of Trees 

There are two basic type of tree from which most lumber is produced. The first type are softwood trees, 
which produce softwood lumber. The softwood lumber industry is primarily geared towards the 
construction industry. Softwood is very plentiful, and coniferous trees grow at a much faster pace 
than hardwood trees. Evergreens or coniferous  trees, are cone-bearing or needle-bearing trees. 
Common examples are pine, fir, cedar, and redwood. 

Hardwood trees are much slower growing, shedding their leaves in fall and , for the most part, 
are dormant throughout the winter months. Hardwood lumber originates from these 
broad-leaf deciduous  trees. Some common hardwoods are walnut, mahogany, maple, birch, cherry, 
and oak. Hardwoods are the preferred choice for the furniture building industry and the flooring industry, 
due to their durability and less likelihood of indentation. 

Trees can be categorized into two basic types,  hardwoods and softwoods. In softwoods, 
the growth rings are composed of both earlywood and latewood. Earlywood is produced in 
the high growth or spring stage, whereas latewood is produced in the latter part of summer and fall. 
Therefore,  earlywood is typically wider within the growth ring.

The hardwood tree has the same annual growth rings, but growth will typically be consistent and 
uniform across the cross-section of the tree trunk.

The outer portion of a tree forms the sapwood, which carry essential nutrients through the tree trunk 
from the root system to the branches and leaves. Every year, the sapwood is replaced with a 
new layer of sapwood, causing the older sapwood to become the outer layer of the heartwood. 
The heartwood does not serve a useful active purpose, but rather, forms the bulk of the tree trunk.

The sapwood is usually much lighter than the heartwood, and is therefore sometimes removed 
from the heartwood before processing.

Knots can be found along boards cut from a tree. The knots are caused by branches which might 
have or might not have successfully grown from the tree trunk. 

                                                                   Moisture Content

 A growing tree contains a high percentage of water. Moisture content (MC),  is given as a percentage 
of the weight of the rest of the lumber. Some moisture is a part of the wood chemistry, but most of it 
lies in the spaces between the cell walls of the bulk of the lumber. After logging, the tree , 
without its' replenishment of water, begins to achieve a state of equilibrium with the 
surrounding atmosphere. Moisture begins to evaporate, and reaches a "equilibrium moisture content" 
(EMC ) relative to the atmosphere. The EMC of wood in a heated room is about 10 percent. 
Freshly felled lumber can be as high as 100 percent

EMC. Once the free moisture has evaporated to within 30 percent EMC, the bound moisture in 
the cells begins to evaporate, and the cell walls shrink, causing the wood to shrink.

This loss of moisture can cause many stresses, triggering splits, and warpage, as well 
as just shrinkage. Moisture movement varies widely between wood species. Artificial drying of lumber, 
or kiln drying, must be controlled as to not cause these stresses in the wood. Wood can also be left 
to air dry, a preferred method, although the drying times are much greater. Sometimes a number 
of years can pass before lumber is at a low enough EMC to be used in furniture.                                                                

More information about this subject is available in our CDROM Woodworking Course


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Last modified: January 20, 2006