Calculating the weight of lumber

      Formulas, detailed instructions and species-specific charts from Professor Gene Wengert. May 3, 2001

by Professor Eugene Wengert

The average weight of 1000 board feet (BF) of lumber can be calculated for a particular species, by following the procedures below. Be aware though, there is considerable variation from load to load of the same species.

Step 1:
Determine the moisture content (MC) at which the lumber was scaled (that is, at which the board foot volume was measured). In the weight calculation equations, this value is called

Remember that moisture content is calculated with the following equation:

Step 2:
Determine the correction factor (CF) that must be applied to the scaled volume to determine the actual volume of wood. Use the following formula:

CF =(actual thickness in inches nominal thickness in inches)
x (actual width in inches nominal width in inches)
x (actual length in feet nominal length in feet)

CF Example 1:
A load of green (freshly sawn) hardwood lumber is 1-1/8" inches thick, but is counted as 1 inch thick when scaled for board footage. The lumber is in random widths, for which the actual and scaled widths are equal. All lumber is 98 inches long (or 8.17 feet), and is scaled as 8 foot. So,

CF=(1.125 1) x (actual width scaled width) x (8.17 8)
=1.125 x 1 x 1.021
=1.149

CF Example 2:
The same scenario as in Example 1, except the lumber is 2-5/32 inches thick (scaled as 2 inches thick) and exactly 14 feet in length. The lumber is again in random widths. So,

CF=(2.156 2) x (actual width scaled width) x (14 14)
=1.078 x 1 x 1
=1.078

CF Example 3:
Planed softwood lumber is scaled as two-by-sixes, although the actual thickness is 1.5 inches and the actual width is 5.5 inches. The two-by-sixes are exactly 12 feet long. Therefore,

CF=(1.5 2) x (5.5 6) x (12 12)
=0.75 x 0.917 x 1
=0.688

Step 3:
Determine the basic weight for

of the desired species

using Table 1 and one of the following formulas:

Step 4:
Apply the board foot correction factor, CF, from equation 2, to arrive at the weight, in pounds, per 1000 BF of lumber, corrected for scaling errors and moisture content:

Step 5:
If the weight of the same lumber at a different moisture content

is desired, use the following formula:

Weight Calculation Examples

Example 1:
What is the weight of 1000 BF of 75% MC, 4/4 northern red oak (scaled thickness = 1 inch), 1-1/8 inches thick and 12 feet long?

Answer:



Example 2:
The lumber in Example 1 is subsequently dried to 6% MC. What is the new weight?

Answer:

Note: This lumber has shrunk about 6% in going from 75% MC to 6% MC, so it is no longer 1000 BF at 6% MC, but about 940 BF. Yet, because it was 1000 BF when measured green, we base the calculations on the green size and weight. If it were rescaled at 6% MC, the calculations would be redone.

Example 3:
What is the weight of 1000 BF of northern red oak that was cut to 1-5/8 inches (1.625") when green, but, when scaled as 6/4 lumber (1-1/2 inches thick) at 6% MC, had actually shrunk to 1-9/16 inches thick (1.5625")?

Answer:



Example 4:
What is the weight of 1000 BF of loblolly pine 2" x 10" x 16' lumber (acual size: 1.5" x 9.25" x 16') at 15% MC? The footage is measured at 15% MC.

Answer:






Table 1. Factors for calculating the weight of wood at different moisture contents. Substitute these numbers for the variables in equation 3.

Untitled Document
Common Lumber Name A B C
Hardwoods
Alder, Red 9.9 19.2 2506
Apple 10.9 31.7 4132
Ash, Black 9.3 23.4 4132
Ash, Green 14.3 27.6 3590
Aspen, Bigtooth 10.3 18.7 2439
Aspen, Quaking 10.3 18.2 2373
Basswood 6.2 16.6 2174
Beech, American 8.9 29.1 3793
Birch, Paper 8.8 25.0 3260
Birch, Sweet 11.9 31.2 4065
Birch, Yellow 9.2 28.6 3723
Buckeye 8.9 17.2 2235
Butternut 11.3 18.7 2440
Cherry 13.8 24.4 3184
Chesnut, American 11.6 20.8 2708
Cottonwood 8.5 16.1 2102
Dogwood 6.8 33.3 4331
Elm, American 10.2 23.9 3116
Elm, Rock 12.2 29.6 3860
Elm, slippery 11.5 25.0 3251
Hackberry 11.8 25.5 3319
Hickory, Bitternut (Pecan) 14.7 31.2 4062
Hickory (True)
Hickory, Mockernut 9.1 33.3 4332
Hickory, Pignut 9.3 34.3 4332
Hickory, Shagbark 10.9 33.3 4333
Hickory, Shellbark 6.6 32.2 4195
Holly, American 8.3 26.0 3387
Hophornbeam, Eastern 7.9 32.8 4266
Laurel, California 15.1 26.5 3456
Locust, Black 21.2 34.3 4470
Madrone, Pacific 7.8 30.2 3925
Maple (Soft)
Maple, Bigleaf 12.8 22.9 2980
Maple, Red 13.1 25.5 3318
Maple, Silver 12.4 22.9 2981
Maple (Hard)
Maple, Black 12.3 27.0 3523
Maple, Sugar 12.3 29.1 3793
Oak (Red)
Oak, Black 11.7 29.1 3792
Oak, California black 16.4 26.5 3455
Oak, Laurel 6.3 29.1 3791
Oak, Northern red 13.6 29.1 3793
Oak, Pin 13.0 30.2 3928
Oak, Scarlet 13.2 31.2 4065
Oak, Southern red 9.6 27.0 3520
Oak, Water 10.4 29.1 3793
Oak, Willow 6.4 29.1 3790
Oak (White)
Oak, Bur 15.4 30.2 3928
Oak, Chestnut 10.1 29.6 3858
Oak, Live 17.5 41.6 5417
Oak, Overcup 10.7 29.6 3860
Oak, Post 11.0 31.2 4063
Oak, Swamp chestnut 10.7 31.2 4063
Oak, White 10.8 31.2

4062

Persimmon 7.0 33.3 4332
Sweetgum 8.9 23.9 3115
Sycamore 10.7 23.9 3115
Tanoak 9.0 30.2 3926
Tupelo, Black 10.4 23.9 3116
Tupelo, Water 12.4 23.9 3115
Walnut 13.4 26.5 3454
Willow, Black 8.6 18.7 2438
Yellow-poplar 10.6 20.8 2708
Common Lumber Name A B C
Softwoods
Baldcypress 13.2 21.9 2844
Cedar, Alaska 14.4 21.9 2844
Cedar, Atlantic white 10.9 16.1 2100
Cedar, eastern red 16.4 22.9 2981
Cedar, Incense 13.1 18.2 2371
Cedar, Northern white 11.1 15.1 1964
Cedar, Port-Orford 12.6 20.2 2641
Cedar, Western red 12.2 16.1 2100
Douglas-fir, Coast type 12.3 23.4 3049
Douglas-fir, Interior west 13.2 23.9 3116
Douglas-fir, Interior north 14.0 23.4 3048
Fir, Balsam 9.9 17.2 2236
Fir, California red 10.6 18.7 2437
Fir, Grand 10.7 18.2 2371
Fir, Noble 10.1 19.2 2507
Fir, Pacific silver 10.4 20.8 2711
Fir, Subalpine 10.5 16.1 2101
Fir, White 12.2 19.2 2506
Hemlock, Eastern 12.6 19.8 2573
Hemlock, Western 11.5 21.8 2847
Larch, Western 11.3 25.0 3251
Pine, Eastern white 12.3 17.7 2303
Pine, Lodgepole 11.5 19.8 2576
Pine, Ponderosa 12.6 19.8 2573
Pine, Red 12.2 21.3 2777
Southern yellow group
Pine, Loblolly 12.9 24.4 3183
Pine, Longleaf 15.0 28.1 3658
Pine, Shortleaf 12.9 24.4 3183
Pine, Sugar 12.6 17.7 2302
Pine, Western white 10.0 18.2 2370
Redwood, Old growth 14.9 19.8 2573
Redwood, Second growth 13.2 17.7 2302
Spruce, Black 11.3 19.8 2575
Spruce, Engelmann 10.0 17.2 2234
Spruce, Red 10.6 19.2 2506
Spruce, Sitka 10.8 19.2 2506
Tamarack 12.0 25.5 3318



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