- Square feet
- Total area (sq ft) you want to cover
- Board width (inches)
- Actual width of one board in inches — not the nominal size on the label
- Width in feet
- Board width divided by 12 to convert inches to feet
- Linear feet
- Running length of material needed before adding waste
Example calculation
Given:
- Room area: 300 sq ft (15 ft × 20 ft)
- Board width: 6 inches
Calculations:
- Board width in feet: 6 / 12 = 0.5 ft
- Linear feet: 300 / 0.5 = 600 linear feet
- With 10% waste: 600 × 1.10 = 660 linear feet (order this amount)
- Boards at 8 ft lengths: ⌈660 / 8⌉ = 83 boards
Coverage check: 600 linear ft × 0.5 ft = 300 sq ft ✓
For a plain-language explanation of why width is required and where the confusion typically starts, see our guide on square feet vs linear feet.
Linear feet measures distance along one direction. Square feet (sq ft) measures area. The board width is the bridge between them: each linear foot of a 6 inch wide board covers exactly 0.5 square feet.
Convert board width from inches to feet by dividing by 12. A 5.5 inch wide deck board is 0.458 feet wide. Divide your square footage by this number to get raw linear feet.
We add 10% waste automatically because cuts at walls, doorways, and the end of each row create offcuts you cannot reuse. Diagonal or herringbone layouts need 15 to 20% instead. Boards with visible defects or mismatched color also get discarded from the usable pile.
The calculator also returns boards needed at three standard lengths: 8, 10, and 12 feet. Lumber yards stock these lengths for most species. Longer boards mean fewer seams in the finished floor, but they are harder to carry and cost more per foot.
Square footage vs linear footage: when to use each
Use square footage when buying anything that ships in coverage units: tile by the box, laminate by the case, or sod by the pallet. Use linear footage when buying anything that ships by length: trim, baseboard, crown molding, deck boards, siding, and fence pickets.
Flooring is the trickiest category because manufacturers list both. Boxes show coverage in square footage, but installers order extra boards by the running foot once they see the room layout. Start with your total area, convert to linear feet, then add waste.
Carpet is sold by the linear foot off a 12 foot wide roll. To convert square feet to linear feet for carpet, divide your room's square footage by 12 (the roll width in feet). A 15 by 20 foot room (300 square feet) needs 25 linear feet of carpet. Your installer will account for seam placement and pattern matching separately.
Converting square feet to linear feet for siding and decking
Siding and decking projects both start with a square footage measurement and end with a linear feet order. For siding, measure the wall area in square feet, then divide by the exposure width of your siding profile. Standard lap siding exposes about 8 inches (0.667 feet) per course, so 500 square feet of wall needs roughly 750 linear feet of siding.
For decking, measure the deck surface area in square feet. A 12 by 16 foot deck is 192 square feet. Using 5.5 inch wide deck boards (0.458 feet), you need 419 linear feet. With 10% waste added, order 461 linear feet of decking. Composite boards often come in 12, 16, or 20 foot lengths, so match your board length to the shortest deck dimension to reduce waste.
Why plank length matters too
Two rooms with the same total area can need different amounts of material. A long narrow hallway uses fewer cuts per row than a small square closet, so the hallway wastes less stock. When your room has one dimension longer than the standard board length, every row has a seam somewhere.
Installers stagger seams so no two rows end at the same spot. The common rule is to offset each row by at least 6 inches from the row above. This stagger eats into the usable length of every board except the first one in each row, which is why the 10% waste factor is a floor, not a ceiling.
For rooms wider than 12 feet, plan on ordering 15% extra. For diagonal or herringbone layouts, order 20%. For reclaimed or character grade wood, order 25% because more boards get culled for defects.
Assumptions and limitations
This calculator assumes one consistent material width across the entire project. If your project mixes widths (for example, a border row of 3.25 inch strips around 5 inch wide planks), run a separate calculation for each width and add the results together.
The 10% waste factor covers straight-lay installations in rectangular rooms. Increase to 15% for L-shaped rooms, 20% for diagonal patterns, and 25% for herringbone. Rooms with many doorways, closets, or angled walls also generate more waste from cuts that cannot be reused.
Results are estimates. Actual material needs vary based on board quality, room layout, and installer experience. Always confirm with your installer or supplier before placing a final order.
Reverse calculation: linear feet to square feet
To go the other direction, multiply linear feet by board width in feet. If you have 400 linear feet of 5.5 inch deck boards: 400 × (5.5 / 12) = 400 × 0.458 = 183 square feet of coverage. The calculator above returns this value as the "Coverage check" line, so you can confirm both directions from one calculation.
This reverse check matters when a lumber supplier quotes you a price per linear foot and you need to know if that quantity will cover your room. Multiply their quote by board width in feet, subtract 10% for the waste you will lose, and compare to your square footage target.
