LUMBER MEASUREMENTS
Lumber.directory Home Owner's Resources: Lumber measurement formulas explained and simplified for the homeowner. Home Owners who can make sense of lumber measurements can make sense of material and contractor invoices, proposals and bids. Contractors who become versatile in converting back and forth can keep their lumber sales people honest. And lumber sales people can offer value by helping their customers with these conversions (many lumber industry lifers cannot convert footage from one point of measure to another). The purpose of this page is to eliminate all of the confusion and discomfort these simple formulas seem to cause. You will read about the most widely forms of traditional lumber measure below. Please reference the Lumber.directory: Glossary of Lumber Terms if you are unfamiliar with some of the terms below.
- Lineal Footage: Lineal footage, or linear footage, refers to the length of the product in running feet. Simple, right? Here's an example: (one) 4x4-16' #1 Doug Fir S4S timber is 16' lineal feet. Despite all of the other information listed in our 16 foot 4x4 Doug Fir post example above, the only descriptor that matters to calculate lineal footage is the length. This is the most commonly used descriptor by retail lumber yards for buying and selling. Lineal footage (abbreviated "LF") is also the simplest lumber measurement term, which usually makes it a good starting point any time you need to convert back and forth between the next two units of measure.
- Board Footage (Also Board Measure): In the example above, we described a 4x4-16' Doug Fir S4S timber. Lineal footage is limited as a term of measure; a 4x4-16 post and a 1/2x6-16 beveled clapboard both have the same measure of LF, but the volume of the two pieces of lumber is much different. Board footage takes the thickness and the width of the lumber into account. The formula is (Thickness X Width X Length)/Divided by 12= BM (or BF). So our formula for Board Footage is: (TxWxL)/12=BM
- Square Footage: Square footage refers to lumber in terms of "coverage," in a practical application sense. For example, if you want to replace your old barnboard plank boards in your 18x10 dining room wall with a clear coated Eastern White Pine look, the square footage of that particular wall is 180 sq feet (LxW=SF) or (HxW=SF). This is important for many reasons. To calculate how much product to order in the example above, you'll need to calculate the square footage for each wall and add them together (make sure to add an additional 5-15% of material for cuts, waste, and even a small amount of discard material). IMPORTANT NOTE: The listed size for a wall or flooring lumber product is NOT the same as the "coverage." Coverage is simply the actual surface area that a wood product will cover after installation. Here's an example from a beautiful interior pine lumber product many will be familiar with: Durgin & Crowell's Enhanced Paneling (check out Enhanced Paneling here). This elegant product offers 1x8 tongue and groove i that actually covers 7". So why is that? There are two contributing factors actually, with each shaving a half inch off the listed eight inches in width. First, mosrt nominal 1x8 wood products, when dressed by the mill to S4S and is ready for home installation, is typically actually 7.5" (see Lumber.directory: Rough & Dressed Lumber & Specialty Lumber Mills). And, with a tongue and groove product, you typically lose another 1/2" for the tongue, meaning the "face" for our Enhanced panel is 7". To continue with the same example, Durgin's 1x6 Enhanced Paneling option offers a 5" coverage, and the 1x5 version offers a 4" face or coverage. The pattern is clear, right? Just subtract an inch from the nominal product description for coverage conversions and square footage calculations. That rule of thumb is not 100%, but if it's not spot on, its at least really close (1/4" or less) much more often than not. (see "Why and What is Nominal Lumber? (In English!) to learn all about actual measurements vs. nominal lumber vs. rough lumber...actually, it's not very interesting, so that page is pretty short. You can probably skip that one, actually.)
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