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Calculate Board Feet


Volume is the Width times the Length time the Height (or thickness) (W x L x H = Volume)

Lumber is sold in Board Feet, although when you visit the lumber yard, and you buy a 2 x 4, it is still priced in Board Feet.

Here we will provide you with information on how Board Feet is Computed.

Board Feet is a measurement of lumber volume.

A board foot is equal to 144 cubic inches of wood. Actually it's easy to calculate using the following formula:

(Thickness x Width x Length) / 144 = Board Feet
1 inch x 1 ft x 1 ft = 1" x 12" x 12" = 144 cubic inches

Lumber has 2 sizes:

When you purchase a 2" x 4" it is in reality a 1 1/2" x 3 1/2"

Example:

The 2" x 4" is the Nominal Size and 1 1/2" x 3 1/2" is the Actual Size

The following Table is for the Nominal and Actual Lumber Sizes

Note:
Lumber is specified by its rough size (nominal). This is why a 1" x 4" board is (actually) 3/4" thick and a 2" x 4" board is actually 1-1/2" thick by 3 1/2".

When you are figuring up board feet, keep in mind a waste factor. If you purchase good clear material add about 15% for waste, if you elect to use lower grade material you will have to allow for defects and more wasted material and should add about 30% for waste.

Common Lumber Sizes:
Nominal Actual Actual - Metric
1" x 2" 3/4" x 1-1/2" 19 x 38 mm
1" x 3" 3/4" x 2-1/2" 19 x 64 mm
1" x 4" 3/4" x 3-1/2" 19 x 89 mm
1" x 5" 3/4" x 4-1/2" 19 x 114 mm
1" x 6" 3/4" x 5-1/2" 19 x 140 mm
1" x 7" 3/4" x 6-1/4" 19 x 159 mm
1" x 8" 3/4" x 7-1/4" 19 x 184 mm
1" x 10" 3/4" x 9-1/4" 19 x 235 mm
1" x 12" 3/4" x 11-1/4" 19 x 286 mm
1-1/4" x 4" 1" x 3-1/2" 25 x 89 mm
1-1/4" x 6" 1" x 5-1/2" 25 x 140 mm
1-1/4" x 8" 1" x 7-1/4" 25 x 184 mm
1-1/4" x 10" 1" x 9-1/4" 25 x 235 mm
1-1/4" x 12" 1" x 11-1/4" 25 x 286 mm
1-1/2" x 4" 1-1/4" x 3-1/2" 32 x 89 mm
1-1/2" x 6" 1-1/4" x 5-1/2" 32 x 140 mm
1-1/2" x 8" 1-1/4" x 7-1/4" 32 x 184 mm
1-1/2" x 10" 1-1/4" x 9-1/4" 32 x 235 mm
1-1/2" x 12" 1-1/4" x 11-1/4" 32 x 286 mm
2" x 4" 1-1/2" x 3-1/2" 38 x 89 mm
2" x 6" 1-1/2" x 5-1/2" 38 x 140 mm
2" x 8" 1-1/2" x 7-1/4" 38 x 184 mm
2" x 10" 1-1/2" x 9-1/4" 38 x 235 mm
2" x 12" 1-1/2" x 11-1/4" 38 x 286 mm
3" x 6" 2-1/2" x 5-1/2" 64 x 140 mm
4" x 4" 3-1/2" x 3-1/2" 89 x 89 mm
4" x 6" 3-1/2" x 5-1/2" 89 x 140 mm

Example:
2" x 4" (Nominal Size) x 10 feet Long
is Actually 1 1/2" x 3 1/2" x 10 feet

therefore;

1.5" x 3.5" x 120" (10 ft x 12" = 120") =
630 cubic inches / 144 cubic inches =
4.375 Board Feet

where 144 cubic inches is 12" x 12" x 1"
which is 1 Board Foot