How do I convert square feet to linear feet for siding?

Formula: Linear feet = Wall square feet × (12 ÷ exposure in inches). Example: 2,000 sq ft of wall at 6″ exposure → 2,000 × 2 = 4,000 linear feet of siding board. Never use nominal board width — always use installed exposure.

How many squares in a carton of siding?

Depends on the profile's exposure. Vinyl D4 (4″ exposure): 2 squares per carton (200 sq ft). Vinyl D5 (5″): 1.6 squares (160 sq ft). HardiePlank 6″ exposure: 1.5 squares (150 sq ft). Board & batten 8″ exposure: 1.2 squares (120 sq ft). Always check the carton label — manufacturers vary.

How many pieces of siding per square?

Formula: Pieces per square = Linear feet per square ÷ board length. Linear feet per square = 1,200 ÷ exposure (inches). Example: 6″ exposure, 12′ boards → (1,200 ÷ 6) ÷ 12 = 200 ÷ 12 ≈ 17 pieces per square.

What is the difference between a board foot and a linear foot?

Linear foot = 12″ of length, regardless of width or thickness. Board foot = volume: 144 cubic inches (12″ × 12″ × 1″). For 1″ × 6″ cedar: 1 linear foot = 0.5 board feet. Wood siding is priced by board foot, but coverage is calculated from exposure in inches.

Why does the siding trade use so many units?

Squares are the standard pricing unit (every contractor speaks it). Cartons are what actually ship from the supplier. Linear feet measure trims (J-channel, corners). Board feet price wood. Pieces are what the installer actually hangs. Converting correctly between them is how you avoid ordering too few or too many.

🔢 Siding Unit Reference

Siding Squares, Cartons & Linear Feet — Unit Conversion Cheat Sheet

The siding trade speaks five units. Learn why each exists, what it measures, and the formula that converts it to any of the other four — with a live converter to test your numbers.

Conversion Cheat Sheet Quick Reference

If you have the wall area already, run it through the main siding calculator and get squares, cartons, trim, and cost in one keystroke. If you just need the unit math without the full calculator, use the live converter below. For profile-specific carton coverage numbers, visit the coverage & exposure calculator. And for step-by-step wall measuring formulas, see the square footage guide.

converter · sq ft → squares → cartons → lf → piecesLive

Wall square feet

Exposure (inches)

Carton coverage (sq ft)

Squares

@ 100 sq ft each

Cartons

rounded up

Linear Ft

4,000

12 ft boards

Pieces

333

at 12 ft each

The Five Units — Defined, Explained, and Traced to Their Origins

Every siding professional carries five units in their head. Here is what each measures, where it came from, and the formula that converts it to the others.

Square Footage (sq ft)

ft²

Width × height

Origin:Basic area measure

Used for:Wall area takeoff, gross and net

One square foot = 12″ × 12″ = 144 sq inches of wall surface.

Square

sq ft ÷ 100

Origin:19th-century roofing trade

Used for:Industry pricing unit, contractor quotes, ordering large quantities

One square = 100 sq ft of installed coverage. The industry has standardized this to normalize between different profile coverages.

Carton / Box

ctn

sq ft ÷ carton coverage, rounded up

Origin:Retail distribution

Used for:What actually ships to your job site

One carton holds a fixed square footage printed on its label — varies by profile from 120–300 sq ft. Always round up.

Linear Feet (lf)

sq ft × 12 ÷ exposure (inches)

Origin:Lumber trade

Used for:Trims (J-channel, corners, starter strip), wood ordering, lap siding board length

One linear foot = 12″ of board length, regardless of width. For lap siding: lf = wall sq ft × (12 ÷ exposure in inches).

Board Feet (bd ft)

bd ft = lf × (thickness ″ × width ″ ÷ 12)

Origin:Wood wholesale

Used for:Pricing and ordering wood siding by volume

One board foot = 144 cubic inches of wood (12″ × 12″ × 1″). Wood siding: bd ft = (thickness × width ÷ 12) × linear feet.

The Complete Conversion Chain — Step by Step

Every siding order follows this chain. Start with wall area, end with what you drive to the supply house. Skip a step and you either waste money or run short.

Wall Square Footage

Net sq ft

walls + gables − openings

Run tape measure, compute each section.

Add Waste Factor

Order sq ft

net × (1 + waste/100)

5–20% depending on roof complexity.

Convert to Squares

Squares

order sq ft ÷ 100

Round up if supplier quotes per square.

Convert to Cartons

Cartons

order sq ft ÷ carton coverage

Round up — partial cartons don't ship.

Convert to Linear Feet

Linear feet

order sq ft × 12 ÷ exposure

For trim ordering (JFchannel, corners).

Convert to Pieces

Pieces

linear ft ÷ board length

For board-count budgeting.

Carton Coverage by Profile — Why They Vary So Much

A vinyl carton covers 200 sq ft. A board-and-batten carton covers 120 sq ft. Same-sized box, 67% less coverage. The difference is exposure — how much of each panel shows after lap overlap. Wider exposure = more coverage per box = fewer boxes.

Profile

Exposure

Carton Coverage

Vinyl D3 (Double 3)

4″

240 sq ft

Vinyl D4 (Double 4)

4″

200 sq ft

Vinyl D4.5

4.5″

180 sq ft

Vinyl D5 (Double 5)

5″

160 sq ft

Fiber Cement (HardiePlank 7.25″)

6″

150 sq ft

Cedar Lap 6″ Clapboard

4.5″

256 sq ft

Corrugated Metal

12″

240 sq ft

Board & Batten (8″ profile)

8″

120 sq ft

The coverage always printed on the carton

These are typical numbers for reference. Manufacturer carton labels are authoritative — always verify on the product you actually plan to buy. Coverage varies by production run, brand, and profile within the same manufacturer's line.

💡 Tip: The exposure shortcut

Linear feet = wall area × (12 ÷ exposure in inches). Memorize this and you can convert between lf and sq ft instantly in your head. For a 6″ exposure: 12 ÷ 6 = 2, so double the sq ft to get linear feet. For 4″ exposure: 12 ÷ 4 = 3, so triple it.

⚠️ Warning: Don't mix nominal with exposure

An 8″ board label doesn't mean 8″ of coverage. Dress down (millwork removes material) plus overlap can reduce exposure by 2–3 inches. Always use installed exposure for all coverage math. The calculator's preset profiles handle this for you.

❌ Don't: Order by board foot without exposure conversion

Wood siding is wholesaled by the board foot but installed by exposure coverage. A 1″ × 6″ cedar board costs the same per board foot whether you install it at 4″ exposure or 6″ exposure — but covers very different wall areas. Always convert through exposure before pricing wood.

More Siding Unit Guides

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Calculate Siding Without Measuring — Photo Upload, Address & Rule of Thumb Estimates

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📏

How to Calculate Square Footage for Siding — Step-by-Step Formula by Wall Type

Precision tutorial: rectangular wall formula, gable formula with roof-pitch rise conversion, irregular wall decomposition, opening deductions, unit conversion chain, and waste factor stacking.