Board Foot vs Linear Foot vs Square Foot: How Lumber Is Priced

Walk into a lumberyard and you'll see three different ways lumber is priced: **board feet** for hardwoods, **linear feet** for trim and dimensional lumber, and **square feet** for plywood and sheet goods. If you don't understand which is which — and more importantly, how to convert between them — you'll either overpay or buy the wrong amount. This guide explains all three units, when each applies, and how to estimate your project needs without getting lost in the math. > **Need a quick board foot estimate?** Use our [free board foot calculator](/board-foot-calculator/) — enter thickness, width, and length to get board feet and total cost instantly. --- ## What Is a Board Foot? The Lumber Industry's Core Unit A **board foot** (abbreviated BF or FBM for "foot board measure") is a unit of lumber *volume* equal to 144 cubic inches. Think of it as a board that's 1 inch thick, 12 inches wide, and 12 inches long: > **1 Board Foot = 1" thick × 12" wide × 12" long = 144 cubic inches** The formula to calculate board feet from any board's dimensions: > **Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12** ### Why Divide by 12? Thickness and width are in inches, and length is in feet. Dividing by 12 converts inches to feet for one of the two cross-sectional dimensions. Here's the same formula decomposed: 1. Cross-sectional area in square inches: Thickness × Width 2. Convert to board feet per linear foot: Cross-section ÷ 12 3. Multiply by length in feet to get total board feet **Example**: A 2"× 6"× 10' board → (2 × 6 × 10) ÷ 12 = **10 board feet**. ### The Quarter System: How Hardwood Thickness Is Named Hardwood lumber uses a cryptic naming convention inherited from the days of rough-sawn mills. Thickness is expressed in quarters of an inch: | Quarter Name | Rough Thickness | Surfaced (S4S) Thickness | Common Uses | |------|:--:|:--:|------| | 4/4 (four-quarter) | 1" | 13/16" | Furniture, cabinets | | 5/4 (five-quarter) | 1-1/4" | 1-1/16" | Deck boards, stair treads | | 6/4 (six-quarter) | 1-1/2" | 1-5/16" | Tabletops, workbenches | | 8/4 (eight-quarter) | 2" | 1-13/16" | Legs, structural members | | 12/4 (twelve-quarter) | 3" | 2-13/16" | Timber frames, mantels | When you buy 4/4 rough-sawn lumber and surface it yourself, you lose about 1/4" to planing and sanding. If you buy S4S (surfaced four sides), the yard has already done the surfacing, and the board is sold at its finished thickness — but you still pay for the rough-sawn board footage. **Important**: Board foot calculations use the *nominal* (rough) thickness, not the finished thickness. A 4/4 board is calculated at 1 inch thick even if you buy it S4S at 13/16". This is why hardwood board footage doesn't match the actual wood volume you receive — you're paying for the sawdust that was removed during surfacing. --- ## What Is a Linear Foot? Length Without Width or Thickness A **linear foot** is simply one foot of length, regardless of the board's width or thickness. A 1×4 and a 2×12 are each one linear foot if they're 12 inches long — even though one contains 5× more wood than the other. ### When Is Lumber Sold by Linear Foot? - **Dimensional construction lumber at home centers**: 2×4s, 2×6s, 2×8s are usually priced per linear foot (or per piece for precut studs) - **Trim and molding**: Baseboards, crown molding, door casing — priced per linear foot regardless of profile width - **Deck boards**: 5/4×6 decking sold per linear foot - **Posts and beams**: 4×4, 6×6 posts priced per linear foot ### Converting Linear Feet to Board Feet If you know the board's cross-section, the conversion is straightforward: > **Board Feet = (Thickness × Width ÷ 12) × Linear Feet** **Example**: 20 linear feet of 2×6 = (2 × 6 ÷ 12) × 20 = 1 × 20 = **20 BF**. The term (Thickness × Width ÷ 12) is called the **board foot factor** — the board feet per linear foot of that cross-section: | Lumber Size | BF per Linear Foot | |------|:--:| | 1×4 | 0.333 | | 1×6 | 0.500 | | 1×8 | 0.667 | | 1×12 | 1.000 | | 2×4 | 0.667 | | 2×6 | 1.000 | | 2×8 | 1.333 | | 2×10 | 1.667 | | 2×12 | 2.000 | | 4×4 | 1.333 | | 6×6 | 3.000 | **The quick mental check**: A 2×6 contains exactly 1 board foot per linear foot. A 1×12 also contains 1 BF per linear foot. Everything else scales proportionally from there. --- ## What Is a Square Foot? Area for Sheet Goods A **square foot** is a unit of area — 12" × 12" = 144 square inches — with no thickness dimension. It's used for materials sold as sheets rather than individual boards. ### When Is Lumber Sold by Square Foot? - **Plywood**: All grades, from 1/4" underlayment to 3/4" hardwood plywood - **OSB and MDF sheets**: Oriented strand board, medium-density fiberboard - **Melamine and particleboard**: Pre-finished shelving material - **Veneer**: Raw wood veneer sold by the square foot **Why not board feet?** Sheet goods have a uniform thickness and price by the sheet, so square footage is the natural unit. A 4'×8' sheet of 3/4" plywood is 32 square feet. Price per square foot ranges from $0.60 (construction-grade OSB) to $4-8 (cabinet-grade hardwood plywood). ### Converting Square Feet to Board Feet (Plywood Equivalent) If you need to compare plywood cost against solid lumber, convert to board foot equivalent: > **Board Feet = Square Feet × Nominal Thickness (inches)** A 4'×8' sheet of 3/4" plywood = 32 sq ft × 0.75" = **24 board-foot equivalent**. This comparison can be eye-opening: 24 BF of solid walnut at $12/BF = $288, while a sheet of walnut plywood at $120 contains the same volume at $5 per equivalent board foot. That's why cabinet makers use plywood for casework and save solid wood for face frames and doors. --- ## Where the Pricing Systems Collide: A Real Lumberyard Comparison Let's say you're building a dining table top — 36" × 72" (18 sq ft) of 6/4 hard maple. Here's how the same project looks in each unit: ### Option A: Buy Rough-Sawn 6/4 Hard Maple by the Board Foot - Target: 18 sq ft at 6/4 (1.5") finished thickness - Rough lumber needed: 20 sq ft (10% surfacing loss) × 1.5" nominal = 30 BF - At $5.50/BF (typical #1 Common hard maple): **$165 for the lumber** - Plus surfacing labor (or pay the yard $0.50-1.00/BF to S4S) ### Option B: Buy 2×6 Construction Lumber by the Linear Foot - 2×6 = 1.0 BF per linear foot, actual size 1.5" × 5.5" - 18 sq ft ÷ (5.5"/12) = ~40 linear feet - At $1.50/LF for kiln-dried SPF 2×6: **$60 for the lumber** - But it's softwood, will dent easily, and boards are 8-16' long with limited width ### Option C: Buy 3/4" Maple Plywood by the Sheet - 18 sq ft = roughly 2/3 of a 4'×8' sheet (32 sq ft) - One full sheet of A1 maple plywood: **$90-120** - Edge-banding needed to hide the plywood edge ($15-25) **The takeaway**: Board foot pricing (Option A) gives you the best material quality for fine furniture. Linear foot (Option B) is cheapest but limits your design. Square foot (Option C) is the middle ground for large, flat surfaces. Understanding all three lets you price a project in any material before you step into the yard. --- ## Hardwood Lumber Grades: Why the Same Species Costs 3× More Hardwood lumber is graded by the **National Hardwood Lumber Association (NHLA)** based on the percentage of clear, defect-free wood recoverable from each board. The same species — say, black walnut — can range from $3/BF to $15/BF entirely because of grade. | Grade | Clear Yield | Typical Price Premium | Best For | |------|:--:|:--:|------| | **FAS (First and Seconds)** | 83%+ | $$$ (baseline) | Fine furniture, visible surfaces | | **FAS 1-Face (F1F)** | 83%+ on best face | $$$ | Projects where only one face shows | | **#1 Common (Select)** | 67-83% | $$ | Kitchen cabinets, painted furniture | | **#2 Common** | 50-67% | $ | Flooring shorts, rustic projects | | **#3 Common** | <50% | $ | Pallet stock, industrial use | **FAS is the gold standard**: boards are at least 6" wide and 8' long, with 83% or more of the board yielding clear, defect-free cuttings. A 6" × 8' FAS walnut board might yield 5.5 BF of clear wood. **#1 Common is the value sweet spot**: you get 67-83% clear yield at roughly 60-70% of the FAS price. For painted cabinets, rustic furniture, or any project where small knots and color variation are acceptable (or desirable), #1 Common is the best value per usable board foot. **The grade ≠ the species quality**: FAS poplar ($3-4/BF) costs less than #2 Common walnut ($6-8/BF) because the underlying species value dominates. Grade refines price *within* a species, but species sets the baseline. ### The 20% Rule for Waste No matter what grade you buy, you cannot use 100% of the board. Defects, end checks, and offcuts consume 15-25% of the lumber you purchase — even at FAS grade. The industry rule of thumb: - **FAS**: Plan for 15-18% waste (knots, sapwood edges, end checking) - **#1 Common**: Plan for 20-25% waste (more frequent defects to cut around) - **#2 Common**: Plan for 30%+ waste (short clear sections between defects) Add your board feet up, then multiply by 1.15-1.30 depending on grade to get your purchase quantity. Our [board foot calculator](/board-foot-calculator/) has a built-in waste factor — dial it up or down based on your wood grade. --- ## 5 Mistakes That Cost You Money at the Lumberyard ### 1. Confusing Linear Feet with Board Feet This is the most expensive mental arithmetic error in woodworking. A 1×12 at $2.00 per linear foot sounds cheap — but it's exactly the same price as $2.00 per board foot (since a 1×12 = 1 BF/LF). However, a 1×4 at $2.00 per linear foot = $6.00 per board foot (since 1×4 = 0.333 BF/LF). Always do the board-foot conversion before comparing prices between different lumber sizes — a "cheap" linear foot price on narrow stock can hide an expensive board-foot price. ### 2. Not Factoring in Surfacing Loss If you buy rough-sawn 4/4 lumber expecting to plane it down to a finished 1" thickness, you'll be disappointed — 4/4 rough typically planes to 13/16" at best, and often closer to 3/4" if the board has any twist. To get a true 1" finished thickness, buy 5/4 rough. The quarter-inch of lost thickness across every board in your project represents 20-25% more board feet you need to purchase to hit your finished dimensions. ### 3. Buying by the Board Instead of by the Project Lumberyards let you pick individual boards, and it's tempting to cherry-pick the widest, clearest boards. But a 10" wide FAS walnut board that's 8' long contains 6.67 BF — and if your project needs 5" wide parts, you'll waste half that board's width. A better approach: calculate your project's **cut list** first (every part's finished dimensions), then work backwards to the rough lumber sizes that minimize waste. Sometimes two narrower boards cost less in total than one wide board because you can nest your parts more efficiently. ### 4. Ignoring the Moisture Content Kiln-dried hardwood (6-8% moisture content) costs 15-25% more than air-dried (12-15% MC), but air-dried wood will continue to shrink after you build with it. Build a table from air-dried maple and bring it into a heated home (4-6% equilibrium MC in winter), and every board in that table will shrink 3-5% across its width — opening gaps in glue joints and cracking breadboard ends. For indoor furniture, kiln-dried is not optional. Air-dried is fine for outdoor projects and utility lumber where seasonal movement is expected. ### 5. Not Checking the Board Before You Buy FAS grade doesn't mean "perfect." Even in a stack of FAS cherry, you'll find boards with sapwood on one edge, small knots near the end, or a slight twist over the length. At the lumberyard, pull each board from the stack, sight down its length for straightness, flip it over to check both faces, and mark defects with chalk so you know where your clear sections begin and end. The 10 minutes you spend sorting through the stack is the difference between 15% and 30% waste at the workbench. No one else is going to do this for you — the yard's job is to sell you boards, not to optimize your yield. --- ## How to Read a Lumberyard Price Sheet A typical hardwood price list looks like this: ``` Species Grade 4/4 5/4 6/4 8/4 Red Oak FAS $3.25 $3.50 $3.85 $4.50 Red Oak #1 Com $2.10 $2.25 $2.50 $3.00 Hard Maple FAS $4.50 $4.75 $5.25 $6.25 Hard Maple #1 Com $3.00 $3.25 $3.60 $4.25 Walnut FAS $9.50 $10.50 $11.50 $14.00 Walnut #1 Com $6.00 $6.75 $7.50 $9.00 Cherry FAS $5.50 $5.75 $6.50 $7.75 Cherry #1 Com $3.75 $4.00 $4.50 $5.25 ``` All prices are per board foot. Thicker stock (6/4, 8/4) commands a premium because thick boards come from larger, older trees that are increasingly scarce. The price jump from 4/4 to 8/4 can be 30-50% for premium species like walnut — which is why thick tabletops are expensive. --- Ready to estimate your lumber needs? Use our [free board foot calculator](/board-foot-calculator/) for instant board foot totals from any dimensions — with quantity, waste factor, and cost built in. Estimating framing lumber? Try the [framing calculator](/framing-calculator/) for wall studs, plates, and headers. Building a deck? The [decking calculator](/decking-calculator/) handles boards, joists, and fasteners.