Square Feet vs Linear Feet

Key Findings

• The width is the whole conversion. linear feet = square feet ÷ width in feet. No width, no conversion — the units measure different things.
• Use the measured face width, not the name. A board called 1×6 is 5-1/2″ wide. Converting 120 sq ft at the name gives 240 lf; at the real width it gives 261.8 lf — and those 240 lf cover only 110 sq ft of your floor. The order has to be 9.1% longer.
• A board foot is neither of these units. It is volume — 144 cubic inches — and thickness is what makes it volume. One ranking calculator calls board feet "the area measurement for lumber" in its own structured data, which is wrong.
• Countertops are linear-priced on an assumed depth. The published residential standard is a 25.5-inch depth (24-inch cabinet plus 1.5-inch overhang), so each linear foot carries 2.125 sq ft. That lets you turn a $65/lf quote into $30.59/sq ft and compare it against a per-sq-ft fabricator.
• Both conversion factors on this page are exact, not rounded. 1 ft = 0.3048 m and 1 ft² = 0.09290304 m² by definition (NIST SP 811), and our calculator's code uses exactly those numbers.
• The calculator embedded below is an area calculator. It cannot output linear feet. The width-based conversion lives on the Sq Ft to Linear Feet Calculator — and its "Deck 5.5″" preset is the measured face width, not the 6-inch name.

The Practical Problem

Two estimates arrive for the same living-room remodel:

• Flooring: $4.50 per sq ft for 180 sq ft = $810.
• Baseboard: $3.25 per linear ft for 54 lf = $175.50.

Those two numbers are not comparable as written, and they shouldn't be. One prices a surface, the other prices a length. Reason about the baseboard in square feet, or the flooring in linear feet, and you get a figure that is either nonsensically low or wildly high. Getting the unit right — and getting the width right inside that unit — is the most common material-ordering error in this category.

The Core Difference

Conversion Formulas

Both directions need the width. Two equivalent forms — pick whichever matches the number you already have:

The inches form is what our linear tool runs internally — areaSqFt * 12 / widthIn (js/extend-calc.js:16-18) — and it is the safer one to do by hand, because board widths are published in inches and dividing by 12 last avoids a rounding step in the middle.

Worked Example 1: The Width Trap — Nominal Name vs Measured Face

This is the error that a correct formula still produces. Lumber is sold under a nominal name that describes the rough-sawn size, not the board you can put a tape on:

Now run the conversion twice for the same 120 sq ft of "6-inch" plank:

1. By the name: 120 × 12 ÷ 6 = 240 lf.
2. By the measured face: 120 × 12 ÷ 5.5 = 261.82 lf.
3. What the short order actually covers: 240 × 5.5 ÷ 12 = 110 sq ft — so 10 sq ft of floor, 8.3% of it, is uncovered.
4. Size of the mistake: 261.82 ÷ 240 = 1.091, i.e. the correct order is 9.1% longer than the name-based answer. Same ratio for decking: 12 ÷ 5.5 = 2.182 lf per sq ft, not 2.000.

Read the same trap in the other direction: a supplier who sells you 240 lf of "6-inch" decking believes they have sold 120 sq ft. They have sold 110. That 9% is why our linear calculator hard-codes its width field in inches and defaults to the measured figures — the "Deck 5.5″" preset is deliberately 5.5, not 6.

Why this matters more than the formula

None of the three conversion pages ranking for this query mention nominal versus actual width at all; they say "material width" or "width in inches" and stop. The formula is not the hard part — the number you feed it is. Flooring sold by the box sidesteps the issue, because coverage per box is stated in square feet; anything you order by the stick does not.

Worked Example 2: Board Feet Are Volume, Not Area

Thick lumber is priced in board feet, and this is where a widely-linked calculator gets it wrong in its own structured data:

Valencia Lumber states it plainly — "A Board Foot is a Measure of Volume… Not length (linear foot), not area (square foot). VOLUME." — and gives the formula: "( Nominal Thickness x Width in Inches x Length in Inches) divided by 144 -OR- ( Nominal Thickness x Width in Inches x Length in FEET) divided by 12". Curtis Lumber publishes a "BOARD FOOTAGE CHART — Board Feet Per Piece" whose columns are nominal sizes (1x2, 1x3, 1x4, 1x5, 1x6, 1x8, 1x10, 1x12, 1x14, 5/4x4, 5/4x6, 5/4x8, 5/4x12, 4x4, 6/4x4, 6/4x6, 6/4x8, 6/4x10) and whose rows are lengths from 8′ to 24′ — volume priced per piece.

Applied: an 8-ft 2×4 is (2 × 4 × 8) ÷ 12 = 5.333 board feet. Check it against the definition: 1.5 × 3.5 × 96 = 504 cu in of the board you actually receive, versus 2 × 4 × 96 = 768 cu in of the board you are billed for — you pay for the nominal size, which is the rough-sawn volume before planing.

Thickness disappears from a sq ft ↔ lf conversion and reappears in board feet. That is the clean way to tell the three units apart — and the reason the claim "dimensioned lumber is sold by linear measurement" is only half true: hardwood is quoted in board feet, and framing lumber at retail is usually quoted per stick at a fixed length rather than per linear foot of face.

This site has no board-foot calculator, so nothing here computes board feet for you — the formula and the worked figures above are the deliverable.

Worked Example 3: Why These Conversions Are Exact, Not Rounded

Most guides in this space treat "12 inches to the foot" as folk arithmetic. It is a definition, and the definitions are retrievable:

• NIST SP 811, Appendix B.6: "In 1959 the definition of the yard was changed to bring the U.S. yard and the yard used in other countries into agreement… Since then the yard has been defined as exactly equal to 0.9144 m, and thus the foot has been defined as exactly equal to 0.3048 m."
• NIST SP 811, Appendix B.8 table: "foot (ft) → meter (m) 3.048 E-01" and "square foot (ft²) → square meter (m²) 9.290 304 E-02", under the note "A factor in boldface is exact."
• Squaring is where the 144 comes from: 0.3048² = 0.09290304 exactly, and 12² = 144 sq in per sq ft exactly. So a sq ft → sq m answer on this site is defensible to eight significant figures, not approximately right.

The exception worth knowing about: there are two feet. NIST: "The name of this foot is 'U.S. survey foot,' while the name of the new foot defined in 1959 is 'international foot.' The two are related to each other through the expression 1 international foot = 0.999 998 U.S. survey foot exactly." The survey foot is 1200 ÷ 3937 = 0.3048006096 m. It is invisible in a bedroom and not invisible in a plat: an acre based on the survey foot is 4,046.873 m² against 4,046.856 m² for the international acre.

Our engine uses in: 1/12 and sqm: 0.09290304 (js/calc-core.js:18, 27) — the same values, so no hidden rounding sits between the calculator's output and the published factors.

Worked Example 4: Countertop Depth, and What a Linear-Foot Price Assumes

A countertop quote in linear feet is an area price with the depth hidden inside it. The hidden number is published:

• Caesarstone US: "While the standard 25.5-inch countertop depth is a good starting point…" and "The standard-depth countertop of 25.5 inches is designed to accommodate the 24-inch base cabinet while providing a functional 1.5-inch overhang."
• SlabWise: "Most retailers and manufacturers who use this method assume a standard 25-inch or 25.5-inch depth, which covers the typical 24-inch base cabinet plus a slight overhang", plus the conversion "Square feet = (linear feet × depth in inches) ÷ 144" and the consequence "A 12-foot kitchen counter quoted at $40/linear foot costs $480, full stop, whether the depth is 24 inches or 26 inches."

Take a 14-ft run (a 10-ft main run plus a 4-ft island) at $65 per linear foot:

1. Total: 14 × 65 = $910, before edges and backsplash.
2. Area at the standard depth: (14 × 25.5) ÷ 144 = 29.75 sq ft.
3. Implied rate: 910 ÷ 29.75 = $30.59 per sq ft.

That last step is the one nobody shows you. $30.59/sq ft is plausible for laminate and implausible for fabricated stone — so a linear-foot quote is only comparable to a per-sq-ft quote after you normalize it. If your depth is not 25.5″, redo step 2 with your depth: at 24″ the same run is 28.0 sq ft ($32.50/sq ft), at 27″ it is 31.5 sq ft ($28.89/sq ft). The linear price never changes; the value you receive does.

Sanity-check a quote that prints both units

Some fabricators print both numbers. At the standard depth each linear foot carries 25.5 ÷ 12 = 2.125 sq ft — SlabWise's own worked job: "240 inches long, so (240 × 25.5) ÷ 144 = 6,120 ÷ 144 = 42.5 square feet total. Each linear foot carries about 2.1 square feet." Divide a linear price by 2.125 to test it: their "$38/LF works out to about $18/sq ft" (38 ÷ 2.125 = $17.88 ✓) and "A granite fabrication quote of $75/sq ft on that same 42.5-square-foot job comes to $3,188 total, or about $159 per linear foot" (75 × 42.5 = $3,187.50; ÷ 20 lf = $159.38 ✓).

Now try their example pair, "$75/sq ft ($230/lin ft)". 230 ÷ 75 = 3.067 sq ft per lf, which implies a depth of 3.067 × 12 = 36.8 inches. Either that job is 37 inches deep or the linear figure carries something the per-sq-ft figure does not (edge profile, seam work, cutouts). That is the question to ask, and you can only ask it because you did the division. Edge work is a real add-on: "another $10 to $25 per linear foot of exposed edge".

Worked Example 5: Trim Is Perimeter, Not Area

A 12 ft × 15 ft room has 180 sq ft of floor and needs crown molding for:

1. Perimeter: 2 × (12 + 15) = 54 lf.
2. Waste for miters: 54 × 1.10 = 59.4 lf — each joint eats 4–6 inches.
3. Sticks: 59.4 ÷ 8 = 7.43 → round up to 8 sticks.

The room's 180 sq ft is irrelevant here, which is exactly the point of the whole guide: two rooms with the same area can need very different trim, and two rooms with the same perimeter can need very different flooring.

One Case Where the Unit Width Is Hidden in the Roll

Carpet is the confusing one: broadloom ships in fixed roll widths, so a retailer can quote it "by the linear foot" and still be quoting area. The width is the roll:

Pages in this query space routinely say "carpet can be sold by linear feet, but you'd need to understand the mathematics" and never print the roll width — which makes the sentence unusable. Ask the width before you accept a linear-foot carpet number; see the carpet calculator for the sq yd conversion (÷9).

What the Calculator on This Page Actually Computes

Be precise about this, because the heading we used to put over the card was wrong: the card below is the area calculator, not a sq ft ↔ linear feet converter.

So the two worked conversions above (240 lf vs 261.8 lf) cannot be reproduced inside the card — use it for the room's area, then convert with the width on the dedicated tool: Sq Ft to Linear Feet Calculator, whose fields are area in sq ft, face width in inches, waste %, and board length in ft, and whose outputs are net linear feet, linear feet with waste, and the number of boards.

Quick reference: square feet to linear feet by face width

Read the "measured" column, not the name column, when you order dimensional lumber or decking.

When Each Unit Wins

Use square feet for

• Flooring by the box — coverage per box is stated in sq ft, so the nominal-width trap never reaches your order.
• Paint — coverage is spec'd per gallon against an area figure.
• Tile — sold per box in sq ft.
• Carpet — area, often converted to sq yd (÷9); see the carpet calculator.
• Roofing — one "square" = 100 sq ft, so "25 squares" is 2,500 sq ft of shingle.
• Real estate — listings report total sq ft; the measurement method is a separate question, covered in how to calculate square footage with inches.

Use linear feet for

• Baseboards, crown molding, quarter round — priced per lf; order the perimeter plus about 10%.
• Gutters and downspouts — a linear run along a roof edge.
• Chain-link and privacy fence — priced per lf of run (buy the pickets by the piece, then check the face width).
• Plumbing, PEX, conduit, wiring — priced per lf.
• Countertop runs — fixed depth, variable length — once you know the depth assumption (price per square foot explains the normalization for floors too).
• Trim on a stair or window — a length, not an area; measure corner to corner.

Volume units live one level up: see square feet vs cubic feet for concrete, mulch and gravel, and the sq ft to cubic feet calculator.

Common Pitfalls

• Converting with the board's name. "6-inch plank" is a 5-1/2-inch face. Order by the name and you are 9.1% short on a decking job. Check the spec sheet or put a tape on it.
• Ordering flooring by linear feet. If a quote says "480 linear feet of 5-inch oak", divide: 480 × 5 ÷ 12 = 200 sq ft. Does that match your room? If not, someone has the width or the unit wrong.
• Forgetting miter waste on trim. A four-corner room still uses ~10% more than the raw perimeter, and long rooms with many joints use more.
• Confusing "square" with "square foot". In roofing one square = 100 sq ft.
• Assuming linear always equals perimeter. Stair nosing is steps × tread width; a counter run is L-shape length plus island length; neither is a room's perimeter.
• Treating a board foot as an area. It is 144 cubic inches of nominal volume — which is why you can't compare it to a square-foot flooring quote at all.
• Accepting two printed prices without dividing them. If a quote shows both $/sq ft and $/lf, the ratio reveals the depth assumption. Ask before you assume they match.

What We Could Not Verify, and Therefore Did Not Cite

Earlier revisions of this page listed three authorities we could not actually read. They are removed rather than softened:

• The ANSI webstore page for the Z765 square-footage standard returned HTTP 403, so this page makes no claim about what that standard requires and does not state its edition year as fact. (Its scope and rounding rules are covered, from documents we could read, in the inches guide.)
• NIST's Handbook 44 landing page returned HTTP 404 from this machine, so no tape-measure tolerance or legal-for-trade definition is quoted here. Every unit definition on this page comes from NIST SP 811 Appendix B, which we did fetch.
• A link to the National Association of Home Builders home page supported nothing specific, so it is gone; the lumber-dimension and countertop-pricing claims are now sourced to the documents that actually state them.
• We did not obtain Lowe's or Home Depot lumber-pricing pages (HTTP 403), so the "framing lumber is quoted per stick at retail" sentence is stated as practice, not as a sourced rate, and no retail price is published on this page.
• No search-engine results page was retrievable from this machine, so this guide makes no claim about its own ranking or any competitor's.

Related Calculators and Guides

Frequently Asked Questions

Sources and How to Check This Page

• ProWood — "Nominal vs Actual Lumber Dimensions" (refetched 2026-10-06, HTTP 200, 153,621 bytes). Verbatim intro: "Lumber sizes are typically sold in nominal measurements. The nominal dimensions refer to the rough-sawn size before it is kiln-dried and planed at the sawmill. The actual dimensions refer to the final size that arrives at the lumberyard." Table rows used above, read from the raw HTML: 1×4 → "3/4″ × 3-1/2″", 1×6 → "3/4″ × 5-1/2″", 1×12 → "3/4″ × 11-1/4″", 2×4 → "1-1/2″ × 3-1/2″", 2×6 → "1-1/2″ × 5-1/2″", 4×4 → "3-1/2″ × 3-1/2″", decking "5/4 x 6" → "1″ × 5-1/2″", "6/4 x 6" → "1-5/16″ × 5-1/2″".
• NIST Special Publication 811, Guide to the SI, Appendix B (refetched 2026-10-06, HTTP 200, 104,716 bytes). Verbatim: "Since then the yard has been defined as exactly equal to 0.9144 m, and thus the foot has been defined as exactly equal to 0.3048 m"; "The two are related to each other through the expression 1 international foot = 0.999 998 U.S. survey foot exactly"; "the factors given are based on the international foot unless otherwise indicated"; table note "A factor in boldface is exact."
• NIST SP 811, Appendix B.8 — factors listed alphabetically (refetched 2026-10-06, HTTP 200, 168,958 bytes). Rows lifted from the table markup: "foot (ft) → meter (m) 3.048 E-01" and "square foot (ft²) → square meter (m²) 9.290 304 E-02". The survey foot's exact value is derived from the same document's statement 1 ft = (1200/3937) m.
• Valencia Lumber & Panel — "What is a Board Foot, anyway??" (refetched 2026-10-06, HTTP 200, 246,775 bytes). Verbatim: "A Board Foot is a Measure of Volume" / "Not length (linear foot), not area (square foot). VOLUME." / "a board that is 1 inch thick by 12" wide by 12" long. (For you math majors, that’s 144 cubic inches…)"; formula as published: "( Nominal Thickness x Width in Inches x Length in Inches) divided by 144 -OR- ( Nominal Thickness x Width in Inches x Length in FEET) divided by 12"; a worked line on the same page, "(4x4x9)/144=1"; and its note that rough-sawn maple "in the rough" measures 15/16" where "The sign will say ‘4/4’".
• Curtis Lumber — "BOARD FOOTAGE CHART, Board Feet Per Piece" (fetched 2026-10-06, HTTP 200, PDF 38,868 bytes). Quoted headers only: the size axis "1x2 1x3 1x4 1x5 1x6 1x8 1x10 1x12 1x14 5/4x4 5/4x6 5/4x8 5/4x12 4x4 6/4x4 6/4x6 6/4x8 6/4x10" and the length axis "Length 8′ … 24′". Individual cell values are deliberately not transcribed — the PDF text layer interleaves the columns, and re-associating them would have been guesswork.
• Caesarstone US — "What is the Standard Depth of Kitchen Countertops?" (refetched 2026-10-06, HTTP 200, 435,026 bytes). Verbatim: "While the standard 25.5-inch countertop depth is a good starting point…" and "The standard-depth countertop of 25.5 inches is designed to accommodate the 24-inch base cabinet while providing a functional 1.5-inch overhang."
• SlabWise — "Per linear foot vs per square foot in countertop pricing" (refetched 2026-10-06, HTTP 200, 250,115 bytes). Verbatim: "Most retailers and manufacturers who use this method assume a standard 25-inch or 25.5-inch depth, which covers the typical 24-inch base cabinet plus a slight overhang"; "Square feet = (linear feet × depth in inches) ÷ 144"; "A 12-foot kitchen counter quoted at $40/linear foot costs $480, full stop, whether the depth is 24 inches or 26 inches"; "(240 × 25.5) ÷ 144 = 6,120 ÷ 144 = 42.5 square feet total. Each linear foot carries about 2.1 square feet. To find the implied per-square-foot price, divide the linear foot price by 2.1"; "A laminate quote of $38/LF works out to about $18/sq ft. A granite fabrication quote of $75/sq ft on that same 42.5-square-foot job comes to $3,188 total, or about $159 per linear foot"; "upgraded edge profiles (another $10 to $25 per linear foot of exposed edge)"; and the printed-pair example 'Some fabricators and home improvement stores print both numbers, for example "$75/sq ft ($230/lin ft)"'. Their own worked arithmetic checks out (20 lf × 12 = 240 in; 240 × 25.5 ÷ 144 = 42.5; $75 × 42.5 = $3,187.50 ÷ 20 lf = $159.38/lf; $38 ÷ 2.125 = $17.88/sq ft). Their printed pair does not collapse to the standard depth: $230 ÷ $75 = 3.067 sq ft per lf ⇒ 36.8-inch depth, which is exactly why this page tells you to divide before you compare.
• Comparator pages reviewed for this revision (all refetched 2026-10-06 and read in raw HTML): Inch Calculator (HTTP 200, 121,844 bytes) — its three worked examples recompute correctly (6/12 = 0.5; 12 × 0.5 = 6; 8 ÷ 0.5 = 16; 3/12 = 0.25; 120 ÷ 0.25 = 480 lf), and its FAQ text quoted in the board-feet section above is verbatim from both the rendered answer and its FAQPage JSON-LD. It also prints "To convert linear footage to square footage, use the following area to length formula: length = area ÷ width" under a square-feet-to-linear-feet heading, which is the reverse of the formula shown. WoodPlank (HTTP 200, 380,319 bytes) — its step text says "Width in Feet: Input the width in inches" while its code is sf = linear / 12 * width, i.e. inches required, so a feet entry is 12× wrong; it also tells users to "Hit 'Calculate'" on a DOM whose only calculator buttons are "Add Row" (it computes on change paste keyup), and its <title> ("SF to LF Calculator") and on-page kicker ("LINEAR FOOT TO SQUARE FOOT CONVERTER") state opposite directions. The Carpet Guys (HTTP 200, 85,765 bytes, "Posted on: September 4th, 2018") — ~3,900 characters of body, one formula-free example (12 × 8 = 96 ✓), and no roll width for the carpet claim it makes; that missing number is supplied in the roll-width table above. None of the three mentions nominal versus actual face width, and none converts a quote between units.
• Attempted, not usable, recorded rather than invented: the ANSI webstore page for Z765-2021 returned HTTP 403 (5,766 bytes), NIST's Handbook 44 landing page returned HTTP 404, Lowe's and Home Depot lumber pages returned HTTP 403, Sherwin-Williams and Benjamin Moore paint pages returned 404, one university board-foot PDF returned 202 with zero bytes, and html.duckduckgo.com returned a 202 challenge page with 0 result links — so this page publishes no coverage-per-gallon figure, no retail lumber rate, no Z765 requirement, no Handbook 44 tolerance, and no ranking claim.
• Re-derive every figure yourself: 120 × 12 ÷ 6 = 240; 120 × 12 ÷ 5.5 = 261.82; 240 × 5.5 ÷ 12 = 110; 261.82 ÷ 240 = 1.091 (9.1% more, and 10 ÷ 120 = 8.3% of the floor uncovered); 12 ÷ 5.5 = 2.182 lf per sq ft vs 12 ÷ 6 = 2.000; 12 ÷ 3.5 = 3.429; 12 ÷ 11.25 = 1.067; 180 × 12 ÷ 5.5 = 392.7 lf of "5/4×6" decking vs 180 ÷ 6 × 12 = 360; (2 × 4 × 8) ÷ 12 = 5.333 bf and 2 × 4 × 96 ÷ 144 = 5.333 bf (same answer, two published forms); 1.5 × 3.5 × 96 = 504 cu in of milled board vs 2 × 4 × 96 = 768 cu in billed; 8 × 5.5 ÷ 12 = 3.67 sq ft of face; 0.3048² = 0.09290304; 1200 ÷ 3937 = 0.3048006096 m; 2 × (12 + 15) = 54; 54 × 1.1 = 59.4; 59.4 ÷ 8 = 7.43 → 8; 14 × 65 = 910; (14 × 25.5) ÷ 144 = 29.75; 910 ÷ 29.75 = 30.59; (14 × 24) ÷ 144 = 28.0 ⇒ 910 ÷ 28 = 32.50; (14 × 27) ÷ 144 = 31.5 ⇒ 910 ÷ 31.5 = 28.89; 25.5 ÷ 12 = 2.125; 480 × 5 ÷ 12 = 200; 100 × 12 = 1,200 and 100 × 15 = 1,500 sq ft of carpet.
• What this page deliberately does not claim: no ranking position for this page or any competitor; no ANSI or Handbook 44 requirement, since neither document was retrievable; no retail price for lumber, flooring, molding, or countertops — the dollar figures above are either arithmetic illustrations (labeled as such) or sentences quoted from their publishers on the dates shown; no statement that hardwood flooring planks shrink from their advertised width (the nominal→actual table is ProWood's dimensional-lumber and decking chart, and flooring sold by the box is quoted in sq ft coverage); no board-foot output from any tool on this site; and the calculator table above describes the widget's own code paths, including its two less-popular behaviors (it clears every result to an em dash on a blank or zero input, and it cannot price per linear foot).