6×6 Lumber Weight by Wood Type & Length • Complete Reference Chart

By Jack Gray, Roof Online Editor • Published October 27, 2022

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6x6 lumber weight - A stack of 6x6 lumber
A stack of 6×6 lumber

6×6 Lumber Weight Factors

6×6 lumber weight depends chiefly on the length of the board, the moisture content of the wood, and which tree species the lumber was made from. Pressure-treating the wood with preservative will also result in a small amount of additional weight after the board has had time to dry out after the treatment process.

Board Length: The length of the 6×6 will obviously be the biggest factor in determining 6×6 lumber weight. This is self-explanatory.

Moisture Content: The moisture content of the wood is a big factor as well, but since all lumber tends to eventually arrive at the air-dried moisture content, variations in moisture content can be considered a temporary consideration.

Green lumber has a higher moisture content than air-dried lumber, and air-dried lumber has a higher moisture content than oven-dried lumber.

Green lumber has a moisture content above 19%. Depending on the actual moisture content of a particular piece of lumber, which can be well above 100% due to the way the moisture content of wood is calculated, a piece of green lumber can be more than 50% heavier than the same piece of lumber when air-dried.

The typical weight of green lumber is roughly 10% to 30% more than the dried weight of lumber made from the same wood species.

Oven-dried wood (also called kiln-dried wood) will normally start with a somewhat lower moisture content than air-dried wood, but it tends to slowly absorb enough moisture from its environment to eventually reach the same moisture content as air-dried wood in the same environment.

Wood Species: The wood species of the tree that the lumber is made from is the third important variable in determining the weight of 6×6 lumber. A 10-foot-long air-dried 6×6 post made out of Douglas Fir (coast type) will weigh about 71 pounds. A 10-foot-long air-dried 6×6 post made out of Sitka Spruce will only weigh around 59 pounds.

Pressure-Treatment: Pressure-treated 6×6 lumber is notoriously heavy at the time that people buy it. This is because when you find it in the store, or at the lumber yard, it is usually freshly-treated, or has had less than a week or two to air dry.

The water weight added to the wood during the pressure-treating process leads to freshly-treated boards weighing up to 75% more than the weight of untreated boards immediately after being treated. This weight is temporary. The board will return (almost) to its original weight as it air-dries during the weeks or months after treatment.

After drying, the weight of a piece of pressure-treated 6×6 lumber will be approximately 0.4% to 1.5% more than the weight of a piece of untreated lumber of the same length and from the same tree species. The preservative in the wood does not add much weight.

Actual Dimensions of 6×6 Lumber

A piece of 6×6 lumber is not six inches by six inches in cross section, despite what it’s called. 6″ x 6″ are the nominal dimensions of the board.

The actual dimensions of a 6×6 are 5.5″ x 5.5″. Here’s why that is:

When a board is first milled, it actually will have the approximate width and depth (the nominal dimensions) that the final piece of lumber will be known by.

After the first rough cut, a six-by-six is, in fact, about six inches by six inches.

The next step in the milling process is to either air-dry or kiln-dry the green lumber, in order to reduce the moisture content of the wood. This causes the boards to shrink, reducing the actual dimensions. One reason this is done is to ensure that when the lumber is finished and sold its dimensions will be stable, and it won’t continue to shrink after somebody buys it.

After drying, the boards are finished by being planed and smoothed, and having their corners slightly rounded.

This reduces the actual dimensions even further; it also lets the lumber producer be certain that the final product has the dimensions required by industry standards. In the case of 6×6 lumber, this industry standard is 5.5″ x 5.5″.

How to Calculate 6×6 Lumber Weight

Step 1Determine the wood type. To determine 6×6 lumber weight, you need to know what kind of wood the 6×6 is made from.

Step 2Look up the density of the wood. Once you know what type of wood you’re dealing with, look up the density of the wood in pounds per cubic foot. Weights of Various Woods Grown in the United States has an extensive table of wood species you can refer to, or there are plenty of other resources on the internet with the same information.

Step 3Calculate the volume in cubic inches of a one-foot-long 6×6. This value will be used to figure out what percentage of a cubic foot a one-foot-long 6×6 is. Since a 6×6 is 5.5 inches by 5.5 inches, a one-foot-long 6×6 will have a volume in cubic inches of 5.5 x 5.5 x 12, or 363 cubic inches.

Step 4Find what percentage of a cubic foot the volume of a one-foot-long 6×6 is. A cubic foot is equal to 12 inches x 12 inches x 12 inches, or 1,728 cubic inches. A 6×6 is 363 cubic inches per foot. 363 is 1/4.7603 of 1,728, or 21.0069% of a cubic foot (363/1728 x 100 = 21.0069).

Step 5Find 21.0069% of the density in pounds per cubic foot of your 6×6 lumber wood species. Let’s say you’re trying to figure out the weight of a 6×6 made out of Douglas fir. You look up the density of Douglas fir and see that it’s 34 pounds per cubic foot. Multiply 34 pounds by 0.210069 to get 7.142346 pounds. (We’d round this to 7.14 to be practical.) This is the weight per foot of a 6×6 post made from Douglas fir.

Step 6Multiply by the length of the 6×6. If your 6×6 is 12 feet long, multiply 12 by 7.14 to get 85.68 pounds.

And there you go, a 12-foot-long Douglas fir 6×6 weighs 85.68 pounds.

About This 6×6 Lumber Weight Chart

The following table provides the approximate weight (dead load, self-weight) of 6×6 lumber produced from the various wood species and in the various lengths normally used in building construction in the US.

The values given in the table are meant to provide a general idea of typical 6×6 lumber weights, and should not be used if precise values are needed for critical engineering calculations. The 6×6 lumber weights are for air-dried lumber; kiln-dried lumber will weigh a little less, and green lumber can weigh a lot more.

When precision is necessary, always refer to the specification sheet for the actual, specific product you intend to use, or contact the technical department of the lumber producer or lumberyard.

You can see 6×6 lumber at the Home Depot. The approximate weights of the actual pieces of lumber for sale are often given in the product descriptions, so this can be a pretty good resource for calculating 6×6 lumber weight.

Table: 6×6 Lumber Weight by Wood Type and Length

6×6 Lumber Weight by Wood Type and Length
(Average Dry Weight, 12% Moisture Content)
Type of Wood Length of 6×6 in Feet (6″ × 6″ × number of feet)
These are the most common wood types
used in construction in North America.
Weight
Per Foot
(6x6x1)
in
Pounds
6x6x6 6x6x8 6x6x10 6x6x12 6x6x14 6x6x16
Pressure
Treated
Wood
Pressure-Treated (Freshly Treated) 15.33 lb 91.98 lb 122.64 lb 153.30 lb 183.96 lb 214.62 lb 245.28 lb
Pressure-Treated (After Air Drying) 8.69 lb 52.14 lb 69.52 lb 86.90 lb 104.28 lb 121.66 lb 139.04 lb
Cedar Western Red Cedar 4.83 lb 28.98 lb 38.64 lb 48.30 lb 57.96 lb 67.62 lb 77.28 lb
Douglas Fir Douglas Fir (Coast Type) 7.14 lb 42.84 lb 57.12 lb 71.40 lb 85.68 lb 99.96 lb 114.24 lb
Douglas Fir (Mountain Type) 6.30 lb 37.80 lb 50.40 lb 63.00 lb 75.60 lb 88.20 lb 100.80 lb
Fir Noble Fir 5.46 lb 32.76 lb 43.68 lb 54.60 lb 65.52 lb 76.44 lb 87.36 lb
Subalpine Fir 4.83 lb 28.98 lb 38.64 lb 48.30 lb 57.96 lb 67.62 lb 77.28 lb
White Fir 5.46 lb 32.76 lb 43.68 lb 54.60 lb 65.52 lb 76.44 lb 87.36 lb
Hemlock Mountain Hemlock 6.93 lb 41.58 lb 55.44 lb 69.30 lb 83.16 lb 97.02 lb 110.88 lb
Western Hemlock 6.09 lb 36.54 lb 48.72 lb 60.90 lb 73.08 lb 85.26 lb 97.44 lb
Larch Western Larch 7.56 lb 45.36 lb 60.48 lb 75.60 lb 90.72 lb 105.84 lb 120.96 lb
Pine Lodgepole Pine 6.09 lb 36.54 lb 48.72 lb 60.90 lb 73.08 lb 85.26 lb 97.44 lb
Ponderosa Pine 5.88 lb 35.28 lb 47.04 lb 58.80 lb 70.56 lb 82.32 lb 94.08 lb
Southern Yellow Pine (Loblolly) 7.98 lb 47.88 lb 63.84 lb 79.80 lb 95.76 lb 111.72 lb 127.68 lb
Southern Yellow Pine (Longleaf) 8.61 lb 51.66 lb 68.88 lb 86.10 lb 103.32 lb 120.54 lb 137.76 lb
Southern Yellow Pine (Shortleaf) 7.98 lb 47.88 lb 63.84 lb 79.80 lb 95.76 lb 111.72 lb 127.68 lb
Southern Yellow Pine (Slash) 10.08 lb 60.48 lb 80.64 lb 100.80 lb 120.96 lb 141.12 lb 161.28 lb
Spruce Engelmann Spruce 4.83 lb 28.98 lb 38.64 lb 48.30 lb 57.96 lb 67.62 lb 77.28 lb
Sitka Spruce 5.88 lb 35.28 lb 47.04 lb 58.80 lb 70.56 lb 82.32 lb 94.08 lb
White Spruce 5.88 lb 35.28 lb 47.04 lb 58.80 lb 70.56 lb 82.32 lb 94.08 lb

About the Author

Jack Gray is a principal roof consultant and vice president at the Moriarty Corporation, an award-winning building enclosure consultant firm founded in 1967. He is also the editor of the Roof Online website.

He has worked in the roofing industry for nearly 25 years, with training and practical experience in roof safety, roof inspection, roof condition assessment, estimating, roof design & specification, roof installation, quality assurance, roof maintenance & repair, and roof asset management.

He was awarded the Registered Roof Observer (RRO) professional credential in 2009.

He also served as an infantry paratrooper in the 82nd Airborne Division and attended Cornell University. Read full bio.


References for 6×6 Lumber Weight