Linear Feet to Square Feet: How to Convert (With a Width Chart)
A linear foot is a length of 12 inches. A square foot is an area. To convert you need the width of the material: square feet = linear feet × width in inches ÷ 12. So 100 linear feet of a 5½ inch board covers 45.8 square feet. The linear feet to square feet calculator converts in both directions.
Square feet in 100 linear feet, by width
| Board width | Square feet in 100 linear ft | Linear feet in 100 ft² |
|---|---|---|
| 1.5 in | 12.5 | 800.0 |
| 2.5 in | 20.8 | 480.0 |
| 3.5 in | 29.2 | 342.9 |
| 5.5 in | 45.8 | 218.2 |
| 7.25 in | 60.4 | 165.5 |
| 9.25 in | 77.1 | 129.7 |
| 11.25 in | 93.8 | 106.7 |
| 12 in | 100.0 | 100.0 |
The formulas
- Linear to square: square feet = linear feet × (width in inches ÷ 12).
- Square to linear: linear feet = square feet ÷ (width in inches ÷ 12).
- Example: 100 ft² of a 5½ inch board = 100 ÷ (5.5 ÷ 12) = 218.2 linear feet, which is 19 boards of 12 ft.
Where it comes up
- Lumber and decking: boards are priced by the linear foot, but you plan by the area of the deck.
- Flooring and siding: use the covered width, which is less than the board width.
- Fencing and trim: pickets and trim are bought by length, and the area they cover is the length times the width.
- Rolls of material: carpet, fabric and landscape fabric are sold by the linear foot off a roll of a given width.
Allow for waste
Add 5 to 15% for cuts and mistakes, and round up to whole boards or boxes. See the waste factor guide. For flooring boxes use the flooring calculator, and for lumber by volume the board foot calculator.
Frequently asked questions
How do you convert linear feet to square feet?
Multiply the linear feet by the width in feet. 100 linear feet of a 5½ inch board is 100 × 5.5 ÷ 12 = 45.8 square feet.
How many square feet in 100 linear feet?
It depends on the width: 100 for a 12 inch board, 45.8 for a 5½ inch board, and 29.2 for 3½ inch trim.
How do you convert square feet to linear feet?
Divide the square feet by the width in feet. For a 5½ inch board, 100 square feet is 218.2 linear feet.
How many linear feet in a square foot?
For a 5½ inch board, 2.18 linear feet. For a 12 inch board, exactly 1.
Should I use the nominal or the actual width?
The actual (or covered) width. A "1×6" is 5½ inches wide, a "2×4" is 3½, and flooring or siding covers less than the board width because of the overlap.
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Estimates only. Quantities depend on your materials, site and supplier. Confirm important numbers before you order, and follow local building codes for anything structural.