CALCULATING THE COSTS OF BUILDING MATERIALS
Calculating Board Footage and Linear Footage and the Cost of Framing Lumber
The purpose of this section is to help you understand how dimensional lumber is bought and sold. Before
covering board footage, here are some of the term and properties associated with framing lumber.
Framing Lumber – The Western Wood Products Association breaks framing lumber into three
categories. Dimension lumber, structural decking and timber grades. We will primarily be working with
dimension lumber. For the purpose of this book, dimension lumber will be defined as 2 by and 4 by
material.
Common terms used in association with framing lumber:
Nominal Size – The dictionary defines nominal as - existing or being something in name only. In
the context of framing lumber, nominal refers to framing lumber’s width and thickness in name
only not actual size. We commonly refer to framing lumber as 24, 26, 28, 210, 212 etc.,
however the actual size or dressed size of the lumber is of lesser dimension. Think of the
nominal size as the size you pay for. Below you will find a chart copied from the WWPA’s
Western Woods Use Book, showing the nominal sizes and actual sizes of the most common
framing lumber.
Standard Lengths – As noted in the table, standard lengths are offered in multiples of 2 feet, such
as - eight feet, ten feet, twelve feet, etc. There are also specialty lengths used for wall studs, 885/8
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and 925/8. When studs of this length are used with a single bottom plate and a double top plate,
wall heights of 7-6 and 8’-0 are attained.
Framing lumber is bought and sold three ways:
 By the linear foot
 By the piece
 By the board foot.
Linear Measure
Linear is defined as a measure of length. This type of measurement does not take into consideration width
and thickness, only length.
Example: The linear measurement of an 8-0 212 is 8-0. Likewise the linear measurement of an 8-0
22 is also 8-0.
At the retail level, framing lumber is typically sold by the piece or by the linear foot.
Examples:
By the piece - 8-0 2x4s cost $4.80 each
By the linear foot - 2x4s cost 60 cents per linear foot.
Board Measure
At the wholesale level, framing lumber is sold by the board foot. Unlike linear measurements, board
footage is a measure of a board’s volume. One board foot can be described as a piece of lumber 12 inches
long, 12 inches wide and 1 inch thick. A board foot measurement is the ratio of a board’s volume compared
to the volume of 1 bd.ft.
12
1
12
Figure. 5-1
One Board Foot
The volume of one board foot, measured in cubic inches, can be calculated as follows:
1 board foot =12121= 144 cu. in.
Therefore any piece of lumber equaling 144 cubic inches is one board foot.
As previously stated, board footage is the ratio or relationship between the volume (LTW) of the board
in question and the volume of one board foot. To better understand this concept, compare the volume of
one linear foot of 24, to one board foot.
Example 5-A: Calculate the number of board feet in one linear foot of 24?
Variables:
L = length expressed in inches
T = thickness expressed in inches
W = width expressed in inches
Equation:
Board in question
One board foot
LTW = 1224 = 96 cu. in.
LTW
12 12 1 144 cu. in.
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Solution:
96 = 8 = .667 bd.ft.
144
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Example 4-1 is offered to help you gain a clear understanding of how board footage is calculated. In reality
the equation may be greatly simplified.
Simplifying The Equation
In order to simplify the equation, express length in feet rather than inches, otherwise board lengths
normally called out in feet must be converted to inches. Next, think of length in units rather than
in feet. For example a 12-0 24 is 12 units long. This will allow the multiplication of feet and
inches.
Now the board foot equation looks like this:
Board Feet = L  T  W
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Example 5-B: Calculate the number of board feet in one linear foot of 24 using feet for
Length.
Variables:
L= length expressed in feet (units)
T = Thickness expressed in inches
W = width expressed in inches
Equation:
L  T  W or 1  2  4 Simplified 1 x 2  4 = .667 bd.ft.
L  T  W
1  1  12
12
Note: The length of one unit could have been left out of the simplified equation but was left in
because lumber most often comes in lengths greater than one foot.
Here are some examples for you to work. Calculate the board footage for one-foot lengths of the following
dimension lumber sizes:
1.
2 x 4 = ___________bd. ft.
2.
2 x 6 = ___________bd. ft.
3.
2 x 8 = ___________bd. ft.
4.
2 x 10 =___________bd. ft.
5.
2 x 12 =___________bd. ft.
Try some more, this time with varying lengths:
6.
One - 8-0” length of 2 x 8 =
__________ bd. ft.
7.
One - 12-0” length of 2 x10 = __________ bd. ft.
8.
One - 14-0” length of 2 x 2 = __________ bd. ft.
9.
One - 10-0” length of 4 x 10 = __________ bd. ft.
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10. One - 8-0” length of 2 x 3 = __________ bd. ft.
11. One - 20-0” length of 4 x14 = __________ bd. ft.
Introducing Quantity (# Of Pieces) Into The Equation
Usually lumber orders will include more than one piece of material therefore, a quantity multiplier must be
part of the calculation. To reflect the total number of board feet in the order, simply place the quantity (#)
into the equation as below.
#  L  T  W = bd. ft.
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Example 5-C: Calculate the board footage of 8 pieces of 10-0 2 x 4
8  10  2  4 = 53.33 Bd. Ft.
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Notice in the next set of questions, the lumber quantities and sizes are written differently. This notation is
universally accepted, fast and reliable. The first number indicates the number of pieces; the second
indicates the length of the pieces; and the ___ x ____ indicates the size of the framing lumber. Hence
12/8 412 would indicate 12 pieces of 412, 8 in length.
Solve these problems
12. 16/10 2 x 4 = __________ bd. ft.
15. 13/8 2x2 = ____________ bd. ft.
13. 10/12 4 x 4 = __________ bd. ft.
16. 28/16 2x14=____________ bd. ft.
14. 15/8 6 x 8 = __________ bd. ft.
17. 56/18 2x3 = ____________ bd. ft.
Introducing Cost to the Equation
Lumberyards selling lumber to homebuilders, contractors, and remodelers typically quote lumber prices by
the thousand. That is, by the cost of one thousand board feet. For example 12-0, 2 x 4s might cost
$575.00 per thousand board feet. You will see this written as 575M.
Definition: M is the Roman numeral for one thousand, hence $575.00 per thousand board feet.
In order to use this information in the equation we need to know the cost of one board foot. By simply
moving the decimal point three places to the left we have the cost of one board foot, $00.575 or
.57 ½ cents. Finally, multiply the calculated board footage by the cost per board foot.
#  L  T W  $/bd. ft. = Board Foot Cost
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Example 5-D: What is the cost of 1/12 24 @575M?
Variables:
# = Number of pieces
L= Length of material
T = Thickness of material
W = width of material
$ = Cost per board foot
Equation:
#  L  T  W = bd. ft.  $ = Board foot cost
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Solution:
1 x 12 x 2 x 4 = 8 .575 = $4.60
A 12-0 2x4 equals 8 bd. ft. and costs $4.60 each.
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Note: As in the example you may find it helpful to first calculate the board footage, write it down, then
multiply by the board foot cost otherwise your equation will only produce the cost.
Try these:
Calculate the board footage and the price of the following lumber quantities:
18.
10/12 22 @ 350M _________
bd. ft.
$___________
19.
22/14 28 @ 590M _________
bd. ft.
$___________
20.
5/18 416 @ 730M _________
bd. ft.
$___________
21.
120/8 24 @ 480M _________
bd. ft.
$___________
22.
19/10 212 @ 610M _________
bd. ft.
$___________
23.
11/12 44 @ 570M _________
bd. ft.
$___________
24.
15/16 46 @ 590M _________
bd. ft.
$___________
25.
8/8 26 @ 590M
bd. ft.
$___________
26.
4/16 410 @ 790M _________
bd. ft.
$___________
27.
2/16 23 @ 488M _________
bd. ft.
$___________
_________
Pricing By The Linear Foot
Finish lumber and trim – Finish lumber is typically used for trim work and is sold by the linear
foot. Working in linear footage makes estimating quantity and price easy. Add up all of the
lengths and number of pieces needed in a particular size and multiply times the cost per foot.
Example 5-E: You need 6/7 1x6 and 14/8 1x2 to complete a set of doorjambs. The 1x6 costs
$1.20 per linear foot and the 1x2 costs $00.67 per Ln. Ft. What is the total cost of the trim
package?
6  7  $1.20= $50.40
14  8  .67 = $75.04
Total = $125.44
Trim, such as base trim, casing, crown molding, and other milled products, are most often priced by the
linear foot.
Try These:
28.
12/16 Colonial Base @ .78 cents/ft. _________
29.
15/8 - 3 1/2 crown @ $9.38/piece
30.
22/8, 11/7, 14/12 - 2 1/2 colonial casing at .56 cents/ln. ft. _________
31.
15 - 2/66/8 pre-hung doors @ $56.00 each ___________
_________
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32.
9/14 - 1x4 @ .68 cent/ft, 12/8 - 1x3 @ .59 cents/ft, 23/16- 1x6 @ $24.00 each. _________
Pricing by the Square Foot
Sheet goods – Plywood, particleboard, drywall, wafer board, etc.; are sold by the square foot or by
the sheet. Most sheet goods are manufactured in 48, 410 and 412 sizes and come in 1/4, 3/8,
1/2, 5/8”,3/4, and 1 thickness’.
Calculating The Cost Of Sheetgoods
Sold by the sheet, no worries. Multiply the number of sheets by the cost per sheet.
Example 5-F: 20 sheets of drywall costing $4.00 per sheet.
20  $4.00 = $80.00
Sold by the square foot –Start with the equation used to find the area of a rectangle.
L  W = Area
Variables:
L = Length
W =Width
# = Number of pieces
$ = Cost per square foot
Equation:
L  W  #  $= cost
Example 5-G: Price 40 sheets of 1/2 4 x 8 CDX plywood costing 500M
Note: Prices per thousand in sheet goods do not take thickness into account. Therefore, move the decimal
point three places to the left and multiply by the calculated square footage.
4  8  40  .50 = $640.00
Price per sheet 4  8  .50 = $16.00
Cost the following materials:
33. 20 sheets of 1/2412 drywall costing 200M _______________
34.
15 sheets of 1/448 Masonite costing 320M _______________
35.
45 sheets of 3/448 CDX plywood costing 560M ____________
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