Sq Ft to Linear Ft Calculator
Convert square feet to linear feet for any strip material. Enter your area and material width to find exactly how many linear feet you need.
How to convert square feet to linear feet
Square feet and linear feet measure different things. Square feet measure a flat area — length times width. Linear feet measure a single dimension of length only. To go from area back to length, you need to know the width of the material you're working with.
The formula is straightforward: divide the total area (in square feet) by the width of each strip (in feet). The result is the total linear feet of material required.
This conversion comes up whenever you're buying strip-style materials — flooring planks, fencing boards, siding panels, roofing panels, or trim. Retailers often sell these products by the linear foot at a specific nominal width, so you need to know exactly how many feet of material to order.
Formula and worked examples
Examples
| Project | Area | Width | LF needed |
|---|---|---|---|
| Hardwood flooring | 300 SF | 3 in | 1,200 LF |
| Lap siding | 1,200 SF | 6 in face | 2,400 LF |
| Metal roofing | 2,000 SF | 36 in | 667 LF |
Common mistakes to avoid
Forgetting to convert inches to feet. Material widths are usually given in inches. If you plug in inches instead of feet in the formula, your result will be 12 times too small. Always divide inches by 12 first.
Not adding a waste factor. Cutting losses are real. Even a simple rectangular room wastes 5–10% of material. Rooms with angles, stairs, or patterns waste 15–20%. Always buy extra.
Confusing nominal and actual width. A 1×6 lumber board has a nominal width of 6 inches but an actual width of 5.5 inches. For flooring, the nominal size is used to describe the plank but the installed face width may differ. When in doubt, measure the actual face width of the material you'll be using.
Forgetting to account for overlap. Siding, roofing, and some fencing products overlap at each course. This means the effective coverage per linear foot is less than the material width. Always use the exposed face width (not total material width) in your calculation.
Frequently asked questions
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Divide the square footage by the width of the material in feet. If the material is 4 inches wide, convert to feet first: 4 ÷ 12 = 0.333 ft. Then: LF = SF ÷ 0.333. So 100 sq ft ÷ 0.333 = 300 linear feet. The formula is always LF = SF ÷ Width(ft).
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Because a square foot is a two-dimensional area and a linear foot is one-dimensional. You need the second dimension (width) to go back from area to length. It is the same reason you cannot find the length of a rectangle without knowing its width.
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Width of 4 inches = 4 ÷ 12 = 0.333 feet. LF = 200 ÷ 0.333 = 600 linear feet. Add 10–15% for waste: you would order about 660–690 linear feet. This assumes straight-run installation without diagonal patterns.
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LF = Wall area (SF) ÷ Siding width (ft). For example, lap siding with a 6-inch exposed face covering 800 sq ft of wall area: LF = 800 ÷ (6÷12) = 800 ÷ 0.5 = 1,600 LF. Always account for window and door openings by subtracting their area from the total wall area.
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Measure the total perimeter of the room in linear feet. That is the approximate linear footage of baseboard or trim needed. For crown molding, measure the perimeter of the ceiling edge. Add 10–15% for waste at corners and cuts. Width of the trim does not affect the linear footage needed for a perimeter run.
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Linear feet (LF) measures only length. Board feet (BF) is a volume unit for lumber: BF = (thickness in inches × width in inches × length in feet) ÷ 12. A 10 ft board that is 2 inches thick and 6 inches wide = (2 × 6 × 10) ÷ 12 = 10 board feet. Board feet account for both dimensions of the cross-section, not just one.
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Divide total linear feet by the plank length. For example, if you need 450 linear feet and planks are 16 feet long: 450 ÷ 16 = 28.125, so you would need 29 planks (always round up). Add waste and cutting allowance as appropriate for the project.
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Yes, for strip materials like metal roofing panels. If panels are 3 feet wide and you need to cover 1,500 sq ft of roof: LF = 1,500 ÷ 3 = 500 LF. For asphalt shingles measured in squares (1 square = 100 sq ft), use the square system directly. Always measure roof slope and calculate actual roof surface area, not just floor area.