Linear Feet to Square Feet Calculator
Both directions, using the one thing the conversion cannot happen without: the width.
Square feet covered
41.7 sq ft
- Each linear foot covers
- 0.417 sq ft
- Bare figure, no waste
- 100.0 lf for 41.7 sq ft
- With 10% waste
- 110.0 lf
- Pieces at 8 ft
- 14 boards
Waste is added to the length, because length is what you buy. Order it in one go — dye lots and mill runs change.
Buying hardwood by the board foot instead? That is a third unit again →
How this is calculated
square feet = linear feet × width(in) ÷ 12 linear feet = square feet ÷ (width(in) ÷ 12) to order = linear feet × (1 + waste%) boards = to order ÷ piece length, rounded up
There is nothing to the arithmetic, and that is the point worth making: linear feet and square feet are not two units of the same quantity, so no conversion factor exists between them. A linear foot measures a length and a square foot an area. The width is the missing dimension that turns one into the other, and a calculator that does not ask for it is assuming a width of twelve inches on your behalf.
Use the covered width rather than the nominal one. Tongue-and-groove flooring loses the tongue into the previous plank, so a board sold as five inches covers something closer to four and a quarter. Dimensional lumber is worse: a 2×6 is 1.5 by 5.5 inches after milling. Ordering on nominal widths under-buys by ten to fifteen per cent, which surfaces at the far wall when the shade no longer matches.
What one linear foot covers, by width
| Width | Per linear foot | 100 lf covers | For 400 sq ft |
|---|---|---|---|
| 2.25 in | 0.188 sq ft | 18.8 sq ft | 2,133 lf |
| 3.25 in | 0.271 sq ft | 27.1 sq ft | 1,477 lf |
| 5.00 in | 0.417 sq ft | 41.7 sq ft | 960 lf |
| 6.00 in | 0.500 sq ft | 50.0 sq ft | 800 lf |
| 7.50 in | 0.625 sq ft | 62.5 sq ft | 640 lf |
| 12.00 in | 1.000 sq ft | 100.0 sq ft | 400 lf |
The last column is the practical one. The same 400 square foot room takes over two thousand linear feet of two-and-a-quarter-inch strip and four hundred of twelve-inch plank — nearly five times the length, five times the cuts and five times the fasteners for identical coverage. Narrow boards are not simply a look; they are a materially longer installation.
Common widths that are not what they say
| Sold as | Actually covers | Under-order if you use the label |
|---|---|---|
| 2×4 lumber | 3.5 in | 13% |
| 2×6 lumber | 5.5 in | 8% |
| 5 in T&G flooring | ≈4.25 in | 15% |
| 6 in lap siding | ≈4.5 in exposure | 25% |
| 12 ft carpet roll | 12 ft, but only in one direction | seam-dependent |
Siding is the worst offender because the number that matters is the exposure — the strip left visible after each course overlaps the one below — and that is never the width printed on the bundle. Carpet is a different problem again: a twelve-foot roll covers twelve feet in one direction only, so a room thirteen feet across needs a seam and an offcut nobody converts their way out of.
Frequently asked questions
How do you convert linear feet to square feet?
Multiply the linear feet by the width in feet. If the width is given in inches, divide it by twelve first. One hundred linear feet of five-inch plank is 100 × 5 ÷ 12, which is 41.7 square feet. That is the entire conversion, and it works in either direction — square feet divided by the width in feet gives you back the linear feet.
Why can't linear feet convert to square feet on their own?
Because they measure different things. A linear foot is a length along one dimension and a square foot is an area across two, so nothing crosses between them without the missing dimension. Asking to convert one to the other without a width is like asking how heavy a mile is. Any calculator that answers without asking for a width is quietly assuming one, usually twelve inches.
What is a linear foot in flooring?
One foot of length along a plank, regardless of how wide that plank is. Lumber yards and mills sell by the linear foot because they cut by length, while flooring is specified by area because that is what the room has. The width printed on the box is what connects the two, and it is why the same order in linear feet buys quite different amounts of floor at three inches versus seven.
Should I use the nominal width or the actual width?
The actual covered width, always. A board sold as six inches wide usually covers about five and a quarter once the tongue is buried in the previous plank, and lumber sold as a 2×6 is really 1.5 by 5.5 inches. Using the nominal figure quietly under-orders by ten to fifteen per cent, which is discovered near the end of the job when the dye lot has changed.
How much waste should I add?
Ten per cent for a straightforward rectangular room laid parallel to the walls, fifteen for a room with several angles or a herringbone pattern, and twenty for a diagonal layout or a floor with many cuts around obstacles. Waste is added to the linear figure rather than the area, because what you buy is length. Long thin rooms waste more than square ones for the same area.
Does this work for fabric, roll goods and siding?
Yes — the arithmetic does not care what the material is, only that it comes in a fixed width. Carpet at twelve feet, vinyl at six, fabric at fifty-four inches and lap siding at whatever the exposure is all follow the same rule. For siding the number that matters is the exposure, the part left visible after the overlap, rather than the full width of the plank.
Planning estimates. Covered widths vary by manufacturer and by profile, and waste depends on the room shape, the layout pattern and how much of the offcut is reusable at the next wall. Measure a sample piece rather than trusting the label, and order the whole job at once.