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4×6 Lumber Weight Calculator & Chart by Wood Type & Length

A stack of pressure-treated pine 4×6 lumber. The weight of these 4×6 beams is around 6 pounds per lineal foot.
A stack of pressure-treated pine 4×6 lumber. The weight of these 4×6 beams is around 6 pounds per lineal foot.

Introduction

Knowing material weights is extremely important when you’re modifying or adding things to a roof. You have to avoid structural loads that exceed the design strength of the roof and the roof’s supporting structure.

I thought it would be helpful to have an easy way to look up the weight of 4×6 lumber, so here it is.

I looked up the densities for the various types of wood used to make dimensional lumber and performed some simple math (I explain the math below after the table) to generate the values used in the calculator and table.

Then I checked the weight values I got against actual product data sheets published by lumber producers and retail stores like Home Depot and Lowe’s to make sure my figures were accurate.

The following calculator and table provides the approximate weight (dead load, self-weight) of 4×6’s produced from the various wood species and in the various lengths (for the table) normally used in building construction in the US.

The values given in the calculator and table are meant to provide a general idea of typical 4×6 weights, and should not be used if precise values are needed for critical engineering calculations. The 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.

4×6 Lumber Weight Calculator

This calculator uses the data presented in the table below for its calculations. It accepts inputs in decimals, so for a 12 foot 6 inch beam, use 12.5; for a 12 foot 3 inch beam, use 12.25, and so on.

4×6 Lumber Weight Calculator

4×6 Lumber Weight Calculator













For the weights of lumber with different dimensions, see my Dimensional Lumber Weight article.

4×6 Lumber Weight Factors

4×6 lumber weight depends chiefly on the length of the beam, 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 4×6 will obviously be the biggest factor in determining 4×6 lumber weight. This is self-explanatory.

Moisture Content: The moisture content of the wood is a big factor as well, but since 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 4×6 lumber. A 10-foot-long air-dried 4×6 beam made out of Southern Yellow Pine might weigh around 55 pounds. A 10-foot-long air-dried 4×6 board made out of White Spruce will only weigh around 37 pounds.

Pressure-Treatment: Pressure-treated 4×6 lumber is famously heavy at the time that people buy it. This is because when you find it in the store or at the lumber yard, it has usually been pressure-treated very recently, and it hasn’t had time to dry out.

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 4×6 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 4×6 Lumber

A piece of 4×6 lumber is not four inches by six inches in cross section, despite what it’s called. 4″ x 6″ are the nominal dimensions of the board.

The actual dimensions of a 4×6 are 3.5″ x 5.5″. Here’s why that is:

One reason is that these are the standard dimensions set by the U.S Department of Commerce and voluntarily agreed to by lumber producers and now expected by builders and consumers.

But why these dimensions exactly? Why aren’t the actual dimensions and the nominal dimensions the same? Well, 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 green four-by-six is, in fact, about four 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. Kiln drying is more common, and results in a little more shrinkage. 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. And in the case of 4×6 lumber, this industry standard is 3.5″ x 5.5″.

How to Calculate 4×6 Lumber Weight

Step 1: Determine the wood type.
To figure out 4×6 lumber weight, you need to know which wood species the 4×6 is made from. In this example, we’ll use Southern Yellow Pine (Longleaf).

Step 2: Look up the density of the wood.
Southern Yellow Pine (Longleaf) is about 41 pounds per cubic foot (lb/ft³). 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 similar information.

Step 3: Calculate the volume in cubic inches of a one-foot-long 4×6.
A nominal 4×6 actually measures 3.5 inches thick by 5.5 inches wide. A piece that is one foot long (12 inches) has:
3.5 inches × 5.5 inches × 12 inches = 231 cubic inches.

Step 4: Find what percentage of a cubic foot that volume is.
A cubic foot is 12 × 12 × 12 = 1,728 cubic inches.
A one-foot 4×6 is 231 cubic inches.
231 ÷ 1,728 = 0.1336.
In percentage terms, that’s about 13.36% of a cubic foot.

Step 5: Multiply that fraction by the wood’s density.
Since Southern Yellow Pine (Longleaf) is 41 lb/ft³, multiply 41 by 0.1336:
41 × 0.1336 ≈ 5.48.
Rounded, that’s about 5.48 pounds per foot for a 4×6 made of Southern Yellow Pine (Longleaf).

Step 6: Multiply by the 4×6’s length.
If your board is 12 feet long, multiply 5.48 lb/ft by 12 ft = 65.76 lb.
Rounded, that’s about 65.8 pounds.

So a 12-foot-long Southern Yellow Pine (Longleaf) 4×6 weighs roughly 65.8 pounds. If you have a different wood species, just substitute its density in Step 5.

Table: 4×6 Lumber Weight by Wood Type and Length

You can scroll this table sideways on smaller screens.
4×6 Lumber Weight by Wood Type and Length
(Average Dry Weight, 12% Moisture Content)
Type of Wood Length of 4×6 in Feet (4 × 6 × number of feet)
These are the most common wood types used in construction in North America. Weight
Per Foot
4×6
× 1 ft

in Pounds
4×6
× 6 ft
4×6
× 8 ft
4×6
× 10 ft
4×6
× 12 ft
4×6
× 14 ft
4×6
× 16 ft
Pressure Treated Wood Pressure-Treated (Freshly Treated) 9.76 lb 58.56 lb 78.08 lb 97.60 lb 117.12 lb 136.64 lb 156.16 lb
Pressure-Treated (After Air Drying) 5.56 lb 33.36 lb 44.48 lb 55.60 lb 66.72 lb 77.84 lb 88.96 lb
Cedar Western Red Cedar 3.07 lb 18.42 lb 24.56 lb 30.70 lb 36.84 lb 42.98 lb 49.12 lb
Douglas Fir Douglas Fir (Coast Type) 4.55 lb 27.30 lb 36.40 lb 45.50 lb 54.60 lb 63.70 lb 72.80 lb
Douglas Fir (Mountain Type) 4.07 lb 24.42 lb 32.56 lb 40.70 lb 48.84 lb 56.98 lb 65.12 lb
Fir Noble Fir 3.48 lb 20.88 lb 27.84 lb 34.80 lb 41.76 lb 48.72 lb 55.68 lb
Subalpine Fir 3.07 lb 18.42 lb 24.56 lb 30.70 lb 36.84 lb 42.98 lb 49.12 lb
White Fir 3.48 lb 20.88 lb 27.84 lb 34.80 lb 41.76 lb 48.72 lb 55.68 lb
Hemlock Mountain Hemlock 4.41 lb 26.46 lb 35.28 lb 44.10 lb 52.92 lb 61.74 lb 70.56 lb
Western Hemlock 3.88 lb 23.28 lb 31.04 lb 38.80 lb 46.56 lb 54.32 lb 62.08 lb
Larch Western Larch 4.81 lb 28.86 lb 38.48 lb 48.10 lb 57.72 lb 67.34 lb 76.96 lb
Pine Lodgepole Pine 3.88 lb 23.28 lb 31.04 lb 38.80 lb 46.56 lb 54.32 lb 62.08 lb
Ponderosa Pine 3.74 lb 22.44 lb 29.92 lb 37.40 lb 44.88 lb 52.36 lb 59.84 lb
Southern Yellow Pine (Loblolly) 5.08 lb 30.48 lb 40.64 lb 50.80 lb 60.96 lb 71.12 lb 81.28 lb
Southern Yellow Pine (Longleaf) 5.48 lb 32.88 lb 43.84 lb 54.80 lb 65.76 lb 76.72 lb 87.68 lb
Southern Yellow Pine (Shortleaf) 5.08 lb 30.48 lb 40.64 lb 50.80 lb 60.96 lb 71.12 lb 81.28 lb
Southern Yellow Pine (Slash) 5.75 lb 34.50 lb 46.00 lb 57.50 lb 69.00 lb 80.50 lb 92.00 lb
Spruce Engelmann Spruce 3.07 lb 18.42 lb 24.56 lb 30.70 lb 36.84 lb 42.98 lb 49.12 lb
Sitka Spruce 3.74 lb 22.44 lb 29.92 lb 37.40 lb 44.88 lb 52.36 lb 59.84 lb
White Spruce 3.74 lb 22.44 lb 29.92 lb 37.40 lb 44.88 lb 52.36 lb 59.84 lb

SPF (Spruce-Pine-Fir) Lumber

Spruce-pine-fir (SPF) lumber is typically considered one product and it’s often used for dimensional lumber. The properties of spruce, pine, and fir lumber are close enough for them to be considered interchangeable for construction purposes. This means that when you buy lumber for framing or similar structural purposes you are likely to get a mixture of wood species from these three tree genera.

The weight of SPF lumber is therefore an average weight that can change depending on the actual mix of wood species in the particular batch you get. Very generally, the average weight of SPF lumber is usually close to the weight of White Spruce or White Fir.

You can read more about the species used for SPF lumber in this article on the American International Forest Products website.

References for 4×6 Lumber Weight

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