Linear feet to square feet
Not a unit conversion. A length becomes an area only when you add a width.
Material estimate
Enter a figure and a width — the conversion needs both.
You need to buy
Use this figure
Worth knowing
What this assumes
A length has no area
Linear feet measure how much board you are buying. Square feet measure how much ground it covers. The width is what connects them, and without one there is nothing to convert — which is why this page asks for it rather than assuming.
And it has to be the actual width
Lumber is named at its rough sawn size and sold surfaced. A 1x6 is 5.5 inches wide, not 6. A 2x4 is 1.5 by 3.5. The name has not matched the measurement for a century, and using the nominal figure here over-states your coverage by around 8 per cent — so you under-order, reliably, and find out on the last row.
Nominal against actual, per 100 linear feet
| Board | Nominal | Actual | Covers | Error if you use nominal |
|---|---|---|---|---|
| 1x4 / 2x4 | 4 in | 3.5 in | 29.17 ft² | 14.3% over |
| 1x6 / 2x6 | 6 in | 5.5 in | 45.83 ft² | 9.1% over |
| 1x8 / 2x8 | 8 in | 7.25 in | 60.42 ft² | 10.3% over |
| 1x10 / 2x10 | 10 in | 9.25 in | 77.08 ft² | 8.1% over |
| 1x12 / 2x12 | 12 in | 11.25 in | 93.75 ft² | 6.7% over |
| 5/4 x 6 decking | 6 in | 5.5 in | 45.83 ft² | 9.1% over |
Actual widths are what a surfaced board really measures. The last column is how much coverage you would think you had — always too much, and always in the direction that leaves you short.
Decking has a gap as well
Boards on a deck are laid with a gap for drainage and movement, so each one covers its own width plus its gap — commonly an eighth of an inch for green lumber and a quarter for dry or composite. That is a row count question rather than a conversion, and the deck calculator handles it properly. Tongue and groove goes the other way: the tongue disappears into the next board, so use the coverage width off the spec sheet rather than the overall width.
Where this goes next
For boards bought by volume rather than by length, the board feet calculator handles hardwood pricing, and the lumber weight calculator tells you what the pile weighs before you try to lift it. For a wall rather than a floor, the board and batten calculator spaces battens evenly across a width and the fence calculator counts pickets with their gaps.
Common questions
How do I convert linear feet to square feet?
Multiply by the width in feet. If the width is in inches — and it usually is — divide it by 12 first. A hundred linear feet of board 5.5 inches wide is 45.83 square feet. There is no conversion without a width, because a length has no area on its own.
Why is the actual width different from the name?
Because lumber is named at its rough sawn size and sold surfaced. A "1x6" leaves the mill at 6 inches and arrives at 5.5 after planing; a 2x4 measures 1.5 by 3.5. The name is a nominal size, not a measurement, and it has not matched reality for a century. Every dimension on the board you are holding is smaller than the number on it.
How much does using the nominal width cost me?
About 8 per cent on a 1x6 and 9 per cent on a 1x8 — you think you have covered more ground than you have, so you under-order. On a 400 square foot deck that is a trip back for the last two boards. The table below gives the error for every common size, and it is always in the same direction.
Why is lumber sold by the linear foot at all?
Because a board is a length of a fixed cross-section, and the mill sells you length. Decking, trim, fencing and framing are all priced that way. What you are covering, though, is an area — so the conversion sits between the price list and the job, and it is where over- and under-ordering happens.
Do I need to allow for the gap between boards?
For decking, yes, and it changes the answer materially. Boards are laid with a gap for drainage and movement — commonly an eighth of an inch for green lumber and a quarter for dry or composite — so each board covers its own width plus its gap. The deck board calculator handles that properly; this page converts a width you give it.
What about tongue and groove?
Use the coverage width, not the overall width. A tongue and groove board loses the tongue into the next board's groove, so a 5.5 inch board might cover only 5 inches once laid. The face or coverage width is usually on the spec sheet, and it is the number that belongs in this calculation.