📐 Construction
Linear to Square Feet
Convert a length and width into square feet, square metres, square yards and board feet. Enter the dimensions, then press Calculate.
About the Linear to Square Feet
Linear feet measure length; square feet measure area. To bridge them you need the other dimension: 12 linear feet of 6-inch board is 6 square feet, because 6 inches is 0.5 ft. Without the width, a linear-foot price cannot be compared with a square-foot price.
For lumber, board feet add thickness: one board foot is 144 cubic inches, or a 1 ft × 1 ft × 1 in board. The formula is thickness (in) × width (in) × length (ft) ÷ 12. This calculator handles the area conversions and the board-foot figure when you supply a thickness.
How the calculation works
- Square feet = length (ft) × width (ft) × quantity.
- Square metres = square feet × 0.09290304.
- Square yards = square feet ÷ 9.
- Board feet = thickness (in) × width (ft) × length (ft) ÷ 12 × quantity.
Reference values
| Dimensions | Square feet | Square metres |
|---|---|---|
| 10 × 10 ft | 100 | 9.29 |
| 12 × 12 ft | 144 | 13.38 |
| 20 × 30 ft | 600 | 55.74 |
| 1 × 10 ft | 10 | 0.93 |
| 4 × 8 ft sheet | 32 | 2.97 |
Worked example: lining a raised bed
A 16 ft × 4 ft raised bed is 64 sq ft. Its perimeter is 40 ft, so one course of edging needs 40 linear ft of board. If the board is 6 inches wide, 40 linear ft covers 20 sq ft—enough for one course around the bed, not for the base. A 2 × 6 × 8 ft board is 2 × 6 × 8 ÷ 12 = 8 board feet.
To compare a linear-foot price with a square-foot price, divide the linear price by the board's width in feet. A $2/linear-ft board that is 0.5 ft wide costs $4/sq ft; a 1 ft wide board at the same price costs $2/sq ft. Without the width, the two prices are not comparable.
Coverage, overlap and nominal widths
Decking and siding are sold by linear foot but installed with overlap or a gap, so the covered area is smaller than the board's nominal area. A 6-inch board used as siding with a 1-inch overlap covers 5 inches of wall, not 6 — a 17% difference. Decking boards are usually spaced a few millimetres apart for drainage, which also reduces coverage slightly.
Work out the covered width first, then divide the wall or deck area by it to get linear feet, and add 10% for cuts and defects. For diagonal or herringbone layouts, add more: the waste rises sharply because every cut end is angled. The board-foot price and the linear-foot price are only comparable once the covered width is known.