Free carpet calculator
Estimate carpet for any room in square feet, square yards, and the linear feet of 12- or 15-foot roll you actually buy — including the roll-width and seam waste that makes carpet cost more than your floor area — updated live, as you type.
On this page14 sections
| Item | Quantity | Est. cost |
|---|---|---|
| Carpet | 41.33 sq yd | $1,157 |
| Pad / underlay | 31.11 sq yd | $156 |
| Installation | 31.11 sq yd | $187 |
Prices are regional estimates: carpet ≈ $28/yd², pad ≈ $5/yd², install ≈ $6/yd². Pad and labor price to the floor area; carpet prices to the purchased area, which includes roll-width waste.
Roll widths, prices and dye lots vary by supplier. How accurate is this?
Results are estimates. Consult a professional.
How the carpet calculator works
Carpet is sold by the square yard and cut from a roll of fixed width, so two numbers drive the order: your floor area and the way whole strips of the roll fall across the room. The calculator multiplies length by width for the area, divides by nine to get square yards, then lays the roll out both ways to find the layout that buys the least carpet. From that it reports the strips, the seams, and the linear feet you purchase.
What the result really means
Three figures do the work. The square-yard area is your floor — the bare minimum if carpet came in any shape. The purchased square yards is what you pay for, because the roll width rarely matches your room exactly and the leftover edge is still on your bill. The linear feet is what the store cuts off the roll. The gap between floor area and purchased area is roll-width waste, and it is built into carpet, not a mistake.
What goes into a carpet estimate
A carpet estimate is built from three pieces: the floor area, the roll width, and a waste margin. Area is simple geometry. The roll width is where carpet stops behaving like paint and starts behaving like fabric off a bolt.
Floor area — the base number
Length times width gives the square feet; dividing by nine gives the square yards retailers quote. This is the part the calculator nails exactly. For an irregular room, split it into rectangles, work out each one, and add them together. Closets and bay windows that get carpet count too.
Roll width — why you buy more than your floor
Carpet comes off a roll that is 12 feet wide as standard, with 15 feet common and 13.5 feet occasional. You buy the full width for whatever length you need, so a room narrower than the roll still costs you the whole width. A room wider than the roll needs a second strip and a seam. Either way, the purchased area is usually larger than the floor area.
Waste factor — the safety margin
On top of the roll-width waste, add a seam-and-pattern allowance for trimming, squaring the cut, and matching a pattern across a seam. Ten percent is the standard default. The calculator adds 10% by default and lets you move it between 0 and 20%.
A worked example using the carpet calculator
Maria is carpeting a 20 ft × 14 ft living room and the carpet she likes comes on a standard 12 ft roll. She wants the floor area, the linear feet to buy, and how much extra a 10% waste margin adds.
Step 1 — Find the floor area
20 × 14 = 280 ft². Divide by 9: 280 ÷ 9 = 31.11 yd². That is the floor — the smallest carpet could ever be.
Step 2 — Lay the roll out both ways
Running strips across the 14 ft width needs ceil(20 ÷ 12) = 2 strips, each 14 ft long: 2 × 14 = 28 linear ft. Running them the other way needs ceil(14 ÷ 12) = 2 strips, each 20 ft long: 2 × 20 = 40 linear ft. The first layout wins: 28 linear ft, 2 strips, 1 seam.
Step 3 — Convert linear feet to what you pay for
28 linear ft off a 12 ft roll is 28 × 12 = 336 ft², or 336 ÷ 9 = 37.33 yd². That is 56 ft² more than the floor — the roll-width waste, baked in before any cutting margin.
Step 4 — Add the seam-and-pattern waste
With 10% added, ceil(28 × 1.10) = 31 linear ft. That is 31 × 12 = 372 ft², or about 41.33 yd². Maria orders 31 linear feet — roughly 41.3 square yards.
How much carpet do I need?
If you want a ballpark before you measure, this table gives the floor area for common room sizes and the carpet to buy off a 12 ft roll with 10% waste. Your own layout can shift the purchased figure, because it turns on how the strips fall.
| Room size | Floor (ft²) | Floor (yd²) | Buy on 12 ft roll (yd², +10%) |
|---|---|---|---|
| 10 ft × 12 ft | 120 | 13.3 | 14.7 |
| 12 ft × 12 ft | 144 | 16.0 | 18.7 |
| 12 ft × 15 ft | 180 | 20.0 | 22.7 |
| 14 ft × 16 ft | 224 | 24.9 | 41.3 |
| 20 ft × 14 ft | 280 | 31.1 | 41.3 |
| 20 ft × 20 ft | 400 | 44.4 | 58.7 |
Purchased figures assume a 12 ft roll, the minimum-waste strip layout, and a 10% seam/pattern margin. Where a room dimension just fits the 12 ft roll (the 10–12 ft rooms above), one strip covers it and waste is small; once both sides clear 12 ft, a second strip and its offcut push the order up sharply — a 15 ft roll undoes much of that for rooms 13–15 ft wide.
Carpet roll width, linear feet, and seams
This is the part most calculators skip, and it is where the money is. Carpet is a roll good, like fabric. The store cuts the full roll width and measures off the length, so the linear feet you buy — not the floor area — is what sets the price.
Reading the roll width
Match the roll width to a room dimension and you cut waste hard. A 12 ft roll covers a 12 ft wide room in one strip with zero side waste. A 13 ft wide room on the same roll needs a second strip and seam, and most of that strip is offcut. A 15 ft roll often solves this, covering a room up to 15 feet wide seam-free.
Why seams are part of the plan
Any room wider than the roll has at least one seam where two strips meet. A seam is a join, sealed with heat-activated tape so the edges do not fray or peel. The Carpet and Rug Institute's installation standard calls for keeping seams to a minimum and sealing every one. Plan them for low-traffic spots, away from doorways and the line of sight from the entry.
| Room width | 12 ft roll | 15 ft roll |
|---|---|---|
| Up to 12 ft | One strip, no seam | One strip, no seam |
| 12–15 ft | Two strips, one seam | One strip, no seam |
| 15–24 ft | Two strips, one seam | Two strips, one seam |
| Over 24 ft | Three or more strips | Two or more strips |
Strip and seam counts for a room of a given width. Picking the roll width that clears your room in one strip is the single biggest waste saver.
Waste factor: how much extra carpet to order
Carpet carries two kinds of waste, and they stack. Knowing which is which keeps you from double-counting or under-ordering.
Roll-width waste comes first
This is the carpet between your room edge and the roll edge — automatic, set by geometry, and already in the purchased figure. You cannot trim it away by ordering carefully; it is the cost of buying a roll good. The calculator shows it as the gap between floor area and purchased area.
Seam and pattern waste sits on top
On top of the roll width, add a margin for trimming the strips square, matching a pattern across a seam, and the odd cutting error. Ten percent is the standard default for a plain carpet in a simple rectangle. Step up to 15% for a bold pattern repeat or a busy, cut-up room, where matching eats more material.
Do stairs, closets, and halls count?
Yes — anything that gets carpet goes into the order. The trap is measuring only the open floor and forgetting the spaces that quietly add yardage.
- Stairs — measure the rise and run of one step, multiply by the number of steps. A standard flight runs about 40–60 ft² (roughly 6–7 yd²). Stairs need their pile running the same way, so add 10–15% for matching.
- Closets — add the closet floor to the room if it gets the same carpet. A walk-in can add a full square yard or two.
- Halls and landings — long, narrow runs are seam-prone; a hall wider than the leftover roll strip may need its own piece.
- Pad / underlay — bought separately by the square yard to the room area, not the roll layout, so it usually costs less per yard than the carpet above it.
For the bare floor area of any of these, the flooring calculator handles box-based products, and a plywood subfloor estimate covers what goes underneath.
Carpet definitions
How accurate is this carpet calculator?
The area math is exact. Length times width, divided by nine, is the precise square yardage of your floor, and the strip layout uses the same minimum-waste logic an installer follows. If your measurements are right, the floor figure is right to the decimal.
The purchased figure is a sound estimate, not a guarantee. It assumes clean rectangles and one continuous roll; a real installer may shift a seam, salvage an offcut for a closet, or split the job across two pieces, which moves the total a little either way. Treat the linear feet and square yards as a confident planning number, confirm the roll width and dye lot with your supplier, and order to the high side — a shortfall in a new dye lot is the one carpet mistake that is hard to fix.
Frequently asked questions about the free carpet calculator
About this carpet calculator
This carpet calculator runs entirely in your browser. Nothing you enter is sent anywhere — the floor area, roll layout, strips, seams, and linear feet all recompute on your device the moment you change a dimension or roll width, so the estimate is instant and private.
It is one of the building and material estimators in our construction calculators collection, part of the wider library of free tools at calculators.