Quick Answer
To convert square feet to linear feet, multiply the area by 12 and divide by the board width in inches: 120 sq ft of 5.5-inch deck boards = 120 × 12 ÷ 5.5 = 261.82 linear feet. Reverse it with sq ft = linear ft × width ÷ 12, and order 5–10% extra for cuts and waste.
Square Feet to Linear Feet Formula (LF = Sq Ft × 12 ÷ Width)
Square feet measure area; linear feet measure length — how boards, trim and rolls are actually sold. The two only connect through the width of the material, which is why every square feet to linear feet conversion starts with the board width:
So 120 sq ft ÷ 5.5-inch boards = 120 × 12 ÷ 5.5 = 261.82 linear ft — and 1 linear ft of that board covers just 0.4583 sq ft.
Use the actual width, not the label on the rack — that trap gets its own section below.
How Many Linear Feet in 100 Square Feet? (By Board Width)
The same 100 sq ft needs wildly different lengths depending on the board — actual dressed widths shown:
| Material (actual width) | Linear ft per 100 sq ft |
|---|---|
| 2¼-in strip hardwood | 533.33 LF |
| 3-in plank | 400 LF |
| 3½-in (a 2×4 or 1×4) | 342.86 LF |
| 5-in engineered plank | 240 LF |
| 5½-in (a “6-inch” deck board) | 218.18 LF |
| 7¼-in (a 1×8) | 165.52 LF |
| 9¼-in (a 1×10) | 129.73 LF |
| 11¼-in (a 1×12) | 106.67 LF |
| 12-in (1 ft) wide | 100 LF |
And typical deck sizes with the standard 5.5-inch board:
| Deck area | Linear feet (5.5-in boards) | With 10% waste |
|---|---|---|
| 120 sq ft (10×12) | 261.82 LF | 288 LF |
| 200 sq ft (10×20) | 436.36 LF | 480 LF |
| 240 sq ft (12×20) | 523.64 LF | 576 LF |
| 320 sq ft (16×20) | 698.18 LF | 768 LF |
| 500 sq ft | 1,090.91 LF | 1,200 LF |
How to Use the Square Feet to Linear Feet Calculator
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Pick the direction.
Tap sq ft → linear ft to turn an area into a length to order, or linear ft → sq ft to see what a length covers.
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Enter the area (or length).
For a deck or floor, multiply the space’s length by its width to get square feet — a 10 × 12 ft deck is 120 sq ft.
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Set the board width.
Type the actual width and pick in or ft. A “6-inch” deck board is 5.5, a 2×4 is 3.5. Leaving gaps? Add the gap: 5.5 board + 0.25 gap = 5.75.
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Read the answer with waste.
The big number is the exact length; the grid shows it with 5% and 10% waste plus yard and meter equivalents. Use Share result to send the order to someone.
The Nominal-Width Trap: “6-Inch” Boards Are Really 5.5 Inches
Lumber is labeled by its nominal size but covers with its actual dressed size — set by the American Softwood Lumber Standard (NIST PS 20). Divide by the label instead of the real width and you under-order on every job: a 120 sq ft deck computed at “6 inches” gives 240 LF, but the boards are 5.5 in, so you actually need 261.82 LF — about 22 LF short (8.3%), before any waste:
| Nominal size | Actual width | Enter in the calculator |
|---|---|---|
| 1×4 / 2×4 | 3½ in | 3.5 |
| 1×6 / 2×6 / 5/4×6 deck board | 5½ in | 5.5 |
| 1×8 | 7¼ in | 7.25 |
| 1×10 | 9¼ in | 9.25 |
| 1×12 | 11¼ in | 11.25 |
Waste Factor: How Much Extra to Order (5–15%)
Every cut end, defect and mis-measure eats material, so suppliers and installers order past the exact math. The working rules: 5% for straight layouts in simple rectangular rooms, 10% for diagonal layouts, stairs, or rooms with many corners, and up to 15% for herringbone and pattern work. The calculator’s grid shows the +5% and +10% totals next to every result — for stair materials specifically, the Stair Stringer Calculator handles the rise-and-run side.
Worked Examples: Deck, Flooring, Paneling & the Reverse
Five conversions exactly as the calculator runs them:
| Scenario | Calculation | Result |
|---|---|---|
| Deck, 120 sq ft, 5.5-in boards | 120 × 12 ÷ 5.5 | 261.82 LF — order 288 LF with 10% waste |
| Same deck with ¼-in gaps | 120 × 12 ÷ 5.75 | 250.43 LF |
| Flooring, 850 sq ft, 5-in planks | 850 × 12 ÷ 5 | 2,040 LF — 2,142 LF with 5% waste |
| Wall paneling, 320 sq ft, 1×8 (7.25 in) | 320 × 12 ÷ 7.25 | 529.66 LF |
| Reverse: what do 100 LF of 5.5-in boards cover? | 100 × 5.5 ÷ 12 | 45.83 sq ft |
