Lumber gets measured three different ways, and the three units share the same last word, which is exactly why so many people mix them up. A linear foot, a square foot, and a board foot describe completely different things about a piece of wood, and confusing one for another is one of the most reliable ways to misread a price, botch an estimate, or order the wrong amount of material.
This guide separates the three cleanly, shows you how to convert between them with simple formulas, and gives you a plain decision rule for which unit belongs to which kind of purchase.
Why lumber has three different feet in the first place
The three units exist because wood gets bought for three different reasons, and each reason cares about a different property of the material. Sometimes you care how far a piece runs, as with trim wrapping a room. Sometimes you care how much surface it covers, as with flooring spread across a floor. And sometimes you care how much actual wood you are getting, as with hardwood stock you will mill into furniture parts. Distance, coverage, and volume are three genuinely different questions, so the trade evolved a unit for each, and all three have survived for the same reason the board foot itself has: each one keeps a particular kind of transaction honest in a way the other two cannot.
None of the three is better than the others in any absolute sense, and that is worth settling right at the start. A linear foot is not a lazy board foot, and a board foot is not an overcomplicated square foot. Each unit is the correct tool for its own question and the wrong tool for the other two. The trouble only starts when a buyer hears one unit and mentally substitutes another, or when two sellers quote the same material in different units and the buyer compares the raw numbers as if they were the same thing.
The shared word “foot” is the villain of the story. It appears in all three names, so the units sound like siblings when they are barely cousins. Once you attach each name to the property it measures rather than to the word foot, the confusion drops away almost completely, and that attachment is precisely what the next three sections are for. A helpful trick while reading them is to mentally replace each unit’s name with the question it answers. Hear linear foot and think how far. Hear square foot and think how much coverage. Hear board foot and think how much wood. Do that consistently for a week of casual reading and the units will never blur together again, because your mind will have stopped filing them under the same misleading word.
The short version: linear foot measures length only. Square foot measures surface area. Board foot measures volume of wood. Three questions, three units.
What a linear foot measures
A linear foot is the simplest of the three: it is one foot of length along a piece, and nothing more. Width does not enter into it. Thickness does not enter into it. If a piece of quarter-round molding runs eight feet along a wall, that is eight linear feet, and the same is true of a massive timber beam of the same length. Linear feet are blind to everything except how far the piece runs.
That blindness is not a flaw; it is the whole point. Linear feet shine for products where the cross-section is fixed and identical from piece to piece. Trim, molding, railing, pipe, cable, gutter, and similar run-based products all have a constant profile, so the only variable that matters to the buyer is how many feet of run they need. Pricing per linear foot lets you measure your walls, add up the runs, and buy exactly that many feet of a known profile.
The unit only becomes dangerous when it is applied to material whose cross-section varies, because then two pieces with identical linear footage can contain wildly different amounts of wood. Sixteen linear feet of narrow screen bead and sixteen linear feet of two-by-twelve are not remotely comparable purchases, even though the linear-foot number is identical. The moment cross-section starts to vary, you have outgrown the linear foot, and one of the other two units needs to take over. There is a simple test for whether the linear foot is safe to use: could you swap any piece in the order for any other piece of the same length without anyone caring? For trim of a single profile, the answer is yes, and linear feet serve perfectly. For a rack of mixed hardwood boards, the answer is obviously no, and the unit has nothing useful left to say.
What a square foot measures
A square foot measures surface area: a patch of coverage one foot by one foot. It adds width to the picture that the linear foot ignored, which makes it the natural unit for anything whose job is to cover a surface. Flooring, decking surface, paneling, siding, sheathing, and sheet goods like plywood are all fundamentally coverage products, so they are naturally described in the unit of coverage.
Notice what the square foot still leaves out, though: thickness. A square foot of half-inch plywood and a square foot of three-quarter-inch oak flooring cover the same area of floor while containing very different amounts of material. For coverage products this is usually fine, because the thickness is standardized within any given product line and already baked into its price. When you buy oak flooring at a price per square foot, the thickness is a known, fixed property of that flooring, so nobody needs a unit that mentions it.
The square foot becomes misleading in exactly one situation: when people treat it as interchangeable with the board foot. The two coincide only for material that is precisely one inch thick, and drift apart for everything else. That relationship is useful enough to deserve its own section with a proper conversion, which is coming shortly. Until then, hold onto the simple observation that area and volume are different kinds of quantity, and no amount of familiarity with one substitutes for the other. A tiled patio and a stack of bricks can involve identical square footage while representing utterly different amounts of material, and wood behaves exactly the same way the moment thickness starts to vary.
What a board foot measures
A board foot measures volume: the actual quantity of wood in a piece, with length, width, and thickness all counted. One board foot is the wood in a block twelve inches long, twelve inches wide, and one inch thick. It is the unit of raw material, which is why hardwood lumber, rough-sawn stock, and slabs are bought and sold this way. When what you are really paying for is wood itself rather than run or coverage, the board foot is the honest measure.
Because volume responds to all three dimensions, the board foot is the only unit of the three that cannot be fooled by shape. A short, wide, thick piece and a long, narrow, thin piece can hold exactly the same board footage, and the unit will price them identically, which is precisely the fairness the lumber trade needs. The other two units would rank those pieces very differently, and both rankings would mislead someone paying for material.
This guide keeps the board-foot recap deliberately brief, because the unit has a full explainer of its own. If the concept is new to you, our primer on what a board foot is builds the mental model from scratch, and the walkthrough on how to calculate board foot covers the formula and its variations in detail. Here, the job is simply to place the board foot in its proper seat beside the other two units. Seen from this comparative angle, its defining feature is completeness. It is the only one of the three that leaves nothing about a piece’s size unaccounted for, which is why every serious conversation about raw lumber eventually lands in board feet no matter which unit the conversation started in.
For any piece where volume is the question, the free Board Foot Calculator turns three measurements into a board-foot count instantly.
The three units side by side
With each unit defined on its own terms, lining them up makes the differences unmistakable. The panels below are worth a slow read, because nearly every unit mistake in the wild comes from forgetting one row of this comparison.
Answers: how far does it run?
Best for trim, molding, railing, and any product with a fixed profile where only the run matters.
Answers: how much does it cover?
Best for flooring, sheet goods, siding, and other coverage products with standardized thickness.
Answers: how much wood is it?
Best for hardwood lumber, rough stock, and slabs, where the material itself is what you are buying.
| Property | Linear foot | Square foot | Board foot |
|---|---|---|---|
| What it measures | Length only | Surface area | Volume of wood |
| Dimensions counted | 1 | 2 | 3 |
| Ignores | Width and thickness | Thickness | Nothing |
| Typical products | Trim, molding, railing | Flooring, plywood, siding | Hardwood lumber, slabs |
| Two equal pieces can differ in wood? | Yes, enormously | Yes, by thickness | No |
| Fair basis for pricing raw wood? | No | Only at fixed thickness | Yes |
Read the bottom two rows twice. They explain nearly everything about why the trade assigns units the way it does. Products with a fixed cross-section can be priced fairly by length. Products with a fixed thickness can be priced fairly by area. Raw wood, which varies in every dimension, can only be priced fairly by volume, and that is the board foot’s entire reason for existing. Keep the table close the first few times you translate a real quote, because seeing the ignores row at the moment of comparison is what prevents the classic slips. Most people do not misconvert; they simply forget that the number in front of them was blind to a dimension that matters, and the table exists to make that blindness impossible to overlook.
Converting linear feet to board feet
The most common conversion question runs from linear feet to board feet, usually because a project plan lists runs of standard-size boards and a supplier prices the same boards by volume, or the reverse. The conversion is a single clean step, provided you know the cross-section of the board in question:
Board feet = Linear feet × (Thickness in inches × Width in inches) ÷ 12The term in the parentheses is doing all the work. It captures the cross-section of the board, which is exactly the information the linear foot throws away. Multiply the cross-section factor by the run and you have restored the missing dimensions, landing back on honest volume. For a two-by-six, the factor is two times six divided by twelve, which is exactly one, so a two-by-six carries precisely one board foot per linear foot of run. That tidy coincidence makes the two-by-six a lovely mental anchor.
Here are the factors for the most common sizes, calculated on their stated dimensions. Multiply your linear footage by the factor and you have board feet.
| Stated size | Board feet per linear foot | Example: 16 linear feet |
|---|---|---|
| 1 × 4 | 0.33 | 5.3 board feet |
| 1 × 6 | 0.50 | 8 board feet |
| 1 × 8 | 0.67 | 10.7 board feet |
| 1 × 12 | 1.00 | 16 board feet |
| 2 × 4 | 0.67 | 10.7 board feet |
| 2 × 6 | 1.00 | 16 board feet |
| 2 × 8 | 1.33 | 21.3 board feet |
| 2 × 10 | 1.67 | 26.7 board feet |
| 2 × 12 | 2.00 | 32 board feet |
Two sizes in that table share a factor of one, and two share a factor of two-thirds, which is a quiet reminder that very different-looking boards can carry identical wood per foot of run. A one-by-twelve and a two-by-six hold exactly the same board footage per linear foot, because doubling the thickness while halving the width leaves the cross-section unchanged. Spotting equivalences like that is a sign the units have genuinely clicked. The factor approach also scales gracefully to whole orders. A cut list with several sizes becomes a short table of runs and factors, each line converting independently, and the board-foot column totals into the material requirement for the entire project. It is the same single multiplication, repeated calmly down a list, which is exactly the sort of arithmetic worth handing to a tool once the list grows long.
Board feet and square feet: the thickness bridge
Board feet and square feet are connected by a single variable: thickness. A board foot is a square foot of material exactly one inch thick, so for one-inch stock the two numbers match perfectly, and every step away from one inch pulls them apart in a completely predictable way. The bridge between them is nothing more than multiplication:
Board feet = Square feet of coverage × Thickness in inches
Square feet of coverage = Board feet ÷ Thickness in inchesRun a few quick examples to feel the bridge in action. Ten square feet of one-inch material is ten board feet, the perfect match. The same ten square feet in inch-and-a-half stock is fifteen board feet, because every square foot of coverage now carries half again as much wood. In two-inch stock it is twenty board feet. Going the other way, twenty board feet of two-inch slab material covers only ten square feet, which is exactly why thick slabs feel so expensive relative to the area they occupy. The material is genuinely there; it is simply stacked vertically where a coverage mindset cannot see it, and the board foot is the unit that refuses to let it hide.
| Thickness | 10 sq ft of coverage equals | 10 board feet covers |
|---|---|---|
| 1 inch (4/4) | 10 board feet | 10 sq ft |
| 1.25 inches (5/4) | 12.5 board feet | 8 sq ft |
| 1.5 inches (6/4) | 15 board feet | 6.7 sq ft |
| 2 inches (8/4) | 20 board feet | 5 sq ft |
| 3 inches (12/4) | 30 board feet | 3.3 sq ft |
One trade convention is worth flagging while we are here. In much of the hardwood world, material thinner than one inch is customarily tallied as a full inch for board-footage purposes, so a bundle of half-inch resawn stock may still be counted at four-quarter. Conventions vary between yards, which is one more reason to confirm how a seller measures before comparing figures. The formulas above give the physical truth; the tally sheet sometimes follows tradition instead.
Nominal sizes and honest conversions
Every conversion in this guide runs on the dimensions you feed it, which raises the question of which dimensions those should be, because construction lumber famously wears two sizes at once. A two-by-four is the name, but the planed board in your hand measures noticeably less in both directions. The name is the nominal size; the tape-measure reading is the actual size, and the gap between them flows straight into any conversion you make.
The practical rule is consistency. Dimensional softwood is conventionally tallied at its nominal size, so the factor table earlier uses stated sizes, matching how such lumber is typically counted. Rough hardwood is generally measured at its true rough dimensions. Surfaced hardwood measures smaller than its rough parent, and which figure a seller quotes varies. None of these conventions is wrong, but mixing them inside a single comparison is how honest numbers turn misleading, so decide at the start of any calculation whether you are working nominal or actual and stay there all the way through.
When a comparison really matters, such as two suppliers quoting what sounds like the same board, ask each one what the measured dimensions are and rerun the conversion on identical footing. It takes a minute and removes the largest source of silent error in cross-unit comparisons. The formulas never lie, but they answer exactly the question you ask, and nominal versus actual changes the question. If this two-sizes situation feels like an unnecessary complication, it helps to remember that both conventions exist for defensible reasons, and the trade functions smoothly on each so long as everyone in a transaction knows which one is in play. The buyer’s only real job is to make sure a conversion never straddles the two without noticing.
Which unit should you use? A plain decision rule
Choosing the right unit stops being hard once you ask what property of the wood your project actually consumes. Everything in the earlier sections collapses into three questions, and whichever one describes your purchase names your unit.
Does only the run matter? If the product has a fixed profile and your plan is a set of lengths, think in linear feet. Trim packages, handrail, edge banding, and stair nosing live here. Measure the runs, add a cutting allowance, and buy the footage.
Does coverage matter? If the product exists to blanket an area and its thickness is standardized, think in square feet. Flooring, paneling, decking surface, and sheet goods live here. Measure the area, add a waste allowance, and buy the coverage.
Does the wood itself matter? If you are buying raw material to mill, shape, or resaw, think in board feet. Hardwood stock, slabs, and rough lumber live here. Total the volume your parts require, add a cushion for waste and defects, and buy the board footage.
Mixed project? Use each unit for its own line item. A single build can sensibly buy framing in linear feet, sheathing in square feet, and walnut for the countertop in board feet. The mistake is not mixing units across items; it is mixing them within one comparison.
Sellers already follow this logic, which is why the units feel attached to product types. You will rarely see slabs priced by the linear foot or crown molding by the board foot, because each product gravitated long ago toward the unit that describes it honestly. Your job as a buyer is simply to recognize the question behind the unit and to translate deliberately whenever two quotes speak different languages. With a little practice the decision stops feeling like a decision at all. You look at a product, the question it answers surfaces on its own, and the right unit follows without conscious effort, the same way an experienced cook reaches for the right pan. The rule stays available for the odd ambiguous case, but the everyday choices become automatic.
Where the units collide in real purchases
Unit confusion is abstract until it lands in an actual quote. These are the collisions that come up constantly, each resolved with the conversions you now have.
The trim job quoted two ways
You need two hundred forty linear feet of one-by-four poplar for a paint-grade trim package. One supplier quotes per linear foot; another sells poplar only by the board foot. Multiply the run by the one-by-four factor of one-third and the job is eighty board feet. Now the second quote can be translated into a linear-foot equivalent, or the first into board feet, and the comparison is finally honest. Without the conversion, the two price tags are not even speaking the same language.
The flooring illusion
A two-hundred-square-foot room needs solid oak flooring, priced per square foot, and a friend points out that raw oak lumber looks cheaper per board foot than the flooring costs per square foot. The bridge formula explains the gap only partly, because flooring thickness under an inch narrows the raw-material difference, and the rest of the flooring price is milling, profiling, and finishing that raw lumber has not received. Converting units shows how much of the premium is material and how much is manufacturing, which is exactly the insight a smart comparison needs.
The deck board translation
A cedar decking option is priced per linear foot for sixteen-foot boards, while a specialty supplier prices similar stock by the board foot. One sixteen-foot board at the stated size converts through the cross-section factor to a board footage, and dividing each supplier’s price by the same unit puts them on level ground. Five minutes of conversion has settled arguments that otherwise run on gut feel and brand loyalty. It also occasionally reveals that the apparent bargain and the apparent splurge were the same price all along, separated only by the units on their tags, which is a small but satisfying vindication of doing the arithmetic before forming the opinion.
Reading a mixed bid
A renovation bid lists framing in linear feet, subfloor in square feet, and stair treads in board feet, and a homeowner asks why the contractor cannot just use one unit. The honest answer is that the bid is already using the right unit for each item, and forcing everything into one unit would make the document less accurate, not more. Understanding the three units well enough to read such a bid comfortably is precisely the fluency this guide is for. It also changes the conversation with the contractor, because questions can now target the substance of each line rather than the unfamiliarity of its unit, which tends to make the whole exchange shorter and considerably more productive for both sides.
Before making a decision, run the numbers with the Waldev board foot tool so both quotes sit in the same unit. A comparison is only as fair as its units are consistent.
Mix-ups that cost real money
Every unit error in the wild is a variation on a small set of patterns. Learn these and you will catch nearly all of them before they reach your wallet.
Comparing a linear-foot price to a board-foot price directly. The numbers are not comparable until one is converted into the other’s unit through the cross-section factor. A lower digit on the tag means nothing across units.
Treating board feet and square feet as identical for thick stock. They match only at one inch of thickness. For eight-quarter material, the board footage is double the coverage, and budgeting by coverage alone will buy half the wood the project needs, a shortfall that has ruined more than one slab-table budget halfway through the build.
Forgetting the width when converting runs. Linear feet carry no width information, so converting them without the actual board width silently invents a number. Always pin down the cross-section before translating a run into volume.
Mixing nominal and actual dimensions in one comparison. Convert both quotes on the same basis, whether nominal or measured, or the tidier-looking number may simply be the one measured more generously.
Assuming the unit from habit rather than the tag. Some yards price small hardwood boards each, some by the linear foot, some by the board foot. Two seconds spent confirming the unit on the tag prevents the most embarrassing version of every mistake above. Yards are generally happy to clarify, and the question marks you as a buyer who knows what to ask rather than one who can be quoted at loosely.
Once the units are straight, the remaining question is what a fair rate looks like. Our guide to lumber prices per board foot covers species ranges and the pricing traps that catch buyers.
Fluent in all three feet
You now hold the full map. Linear feet answer how far, square feet answer how much coverage, and board feet answer how much wood, with clean formulas bridging any two of them whenever a purchase demands a translation. That fluency is quietly valuable every time you read a tag, compare two suppliers, or plan a project that mixes trim, sheet goods, and raw lumber in a single bill of materials.
The board foot remains the deepest of the three units, simply because volume has more moving parts than length or area, and the rest of this cluster covers it from every side. For the concept, the primer on what a board foot is lays the foundation. For yield from round timber, the walkthrough of the log board foot calculator covers scaling rules. And for any real piece in front of you, you can estimate this faster with the free calculator.
Whenever a comparison needs a board-foot figure, the free Board Foot Calculator produces it from three measurements in a second, leaving you to focus on the decision itself.
Frequently asked questions
What is the difference between a board foot and a linear foot?
A linear foot measures length only, ignoring width and thickness entirely, while a board foot measures the volume of wood, counting all three dimensions. Sixteen linear feet of narrow trim and sixteen linear feet of thick, wide plank are identical in linear feet but contain vastly different amounts of wood, and therefore very different board footage. Use linear feet for fixed-profile products where only the run matters, and board feet when the quantity of wood itself is what you are buying.
How do I convert linear feet to board feet?
Multiply the linear footage by the board’s cross-section factor, which is thickness in inches times width in inches divided by twelve. For a two-by-six, that factor is exactly one, so every linear foot carries one board foot. For a one-by-four it is one-third, so sixteen linear feet works out to about five and a third board feet. The conversion restores the width and thickness information that the linear foot ignores, turning a run into an honest volume.
Is a board foot the same as a square foot?
Only when the material is exactly one inch thick. A square foot measures surface coverage with no thickness, while a board foot measures volume that assumes an inch of thickness. For one-inch stock the two numbers match, but for thicker material the board footage exceeds the coverage, and for thinner material the physical volume falls below it. Treating the two as interchangeable for anything other than one-inch stock is one of the most common unit mistakes in lumber buying.
How do I convert board feet to square feet?
Divide the board footage by the thickness in inches to get square feet of coverage, or multiply square feet by the thickness to get board feet. Twenty board feet of two-inch slab material covers ten square feet, while twenty board feet of one-inch stock covers twenty square feet. The thickness is the entire bridge between the two units, which is why you must know it before converting in either direction.
Why is some lumber sold by the linear foot and some by the board foot?
Products with a fixed, identical cross-section, such as trim and molding, can be priced fairly by length alone, so they sell by the linear foot. Raw lumber varies in width and thickness from piece to piece, so a fair price must account for the actual volume of wood, which is what the board foot measures. Each product type gravitated toward the unit that describes it honestly, which is why the units feel attached to particular kinds of material.
How many board feet are in a linear foot of a 2×6?
Exactly one. The cross-section factor for a two-by-six is two times six divided by twelve, which equals one, so each linear foot of run carries one board foot of wood. This makes the two-by-six a convenient mental anchor for conversions. A one-by-twelve shares the same factor of one, since halving the thickness while doubling the width leaves the cross-section, and therefore the board footage per foot of run, unchanged.
Do square feet account for thickness?
No. A square foot measures area only, so it says nothing about how thick the material is. Coverage products like flooring and plywood are sold by the square foot precisely because their thickness is standardized within each product line and already reflected in the price. The moment thickness varies and matters to the purchase, area alone stops being a fair measure, and the board foot, which counts thickness, becomes the appropriate unit.
Which unit should I use to compare two lumber quotes?
Convert both quotes into the same unit before comparing, and for raw wood that unit should usually be the board foot, since it reflects the actual material. Confirm the measured dimensions each seller uses, apply the cross-section factor to any linear-foot price, and bridge any square-foot figure through the thickness. Comparing prices across different units without converting is the single most reliable way to draw the wrong conclusion from two honest quotes.
Translate any quote in seconds
The three feet stop being confusing the moment you name the question each one answers, and from there every conversion is a single multiplication. When a real purchase puts two units in front of you, run the numbers with the Waldev Board Foot Calculator — the guide explains the units, and the calculator helps you put the comparison on level ground.
Disclaimer: The conversion factors and examples in this guide are illustrative and use stated sizes for clarity. Actual lumber dimensions, tally conventions, and pricing bases vary between suppliers and regions, so always confirm measured dimensions and the unit of sale before comparing quotes or placing an order.
