Carpet Calculator: How Much Carpet Do I Need?

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A 14 x 11 ft room is 154 sq ft of floor (17.11 sq yd), but carpet comes off a roll of fixed width: order one 14.5 ft piece of 12 ft wide carpet, 19.33 sq yd (174 sq ft).

How much carpet do you need?

Enter the room size wall to wall. Carpet comes off a roll 12 or 15 ft wide, so we lay full-length pieces side by side, add trim at each wall, and pick the direction that uses less carpet unless you choose one. Try both roll widths.

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Pieces run full length side by side with the pile the same way, with at least 3 in to trim at each wall (CRI 105 installation standard). Seams run the way the pieces do. Patterned carpet needs extra for matching, and an installer's seam plan can differ.

Rolls come in widths such as 12 or 15 ft, and the carpet needs at least 3 in to trim at each wall. Rule of thumb: one 12 ft piece covers a room up to 11 ft 6 in wide, and one 15 ft piece up to 14 ft 6 in.

Our carpet calculator lays full-length pieces side by side, adds the trim, and picks the direction that uses less carpet.

How to measure a room for carpet

  1. Measure the length and width wall to wall at the widest points, to the nearest inch, and convert to decimal feet (11 ft 6 in is 11.5 ft; see our square footage calculator). Replacing the baseboard too? The baseboard calculator uses the same length and width.
  2. Treat closets and alcoves as separate rectangles and run each one. That overestimates a little, since an installer may cut a closet from offcuts.
  3. Decide which way the seams should run (see below) and set the direction if needed.
  4. Check the roll width of your style, and try both 12 and 15 ft.

How the calculator lays out carpet

It follows the Carpet and Rug Institute's residential standard, CRI 105, and The Home Depot's installation guide:

  • Full-length pieces, pile the same way. CRI 105 says: "Where two or more pieces of the same broadloom carpet are adjacent, the pile direction is required to be the same unless otherwise specified." Home Depot's guide says the same. A leftover strip can't be turned sideways to fill a gap, so every piece runs the full length.
  • Trim at every wall. CRI 105 asks for "at least 3 inches along each wall for trimming," and Home Depot says to measure along the longest wall and "Add 6 inches to the measurement." Each piece is cut 6 in longer than the room, and the pieces together span the other dimension plus 6 in.
  • Roll widths. Shaw Floors' catalog filters carpet by 12 ft and 15 ft widths, and some styles, such as Awaken Spirit II, come in both. Home Depot sells TrafficMaster Viking "12 ft. Wide x Cut to Length."
  • Direction. It takes whichever way orders less carpet and shows the other total, so you can choose by seam placement. It also says when the other roll width needs fewer pieces, since CRI 105 says to "Keep seams to a minimum."

So you order more carpet than floor. The calculator doesn't plan fill pieces or cross seams (none of these sources give rules for them), so an installer's seam plan can use less.

The carpet formula

  • Pieces = (room size across the pieces + 2 × trim) ÷ roll width, rounded up
  • Piece length = room size along the pieces + 2 × trim
  • Linear ft = pieces × piece length × (1 + extra % ÷ 100)
  • Sq ft = linear ft × roll width; sq yd = sq ft ÷ 9
  • Floor and pad = room length × room width

Worked example (the calculator's default values)

A 14 x 11 ft room, 12 ft roll, automatic direction, 3 in trim (0.5 ft per dimension), and 0% extra:

  1. Along the length: 11.5 ft across fits one piece, 14.5 ft long: 174 sq ft.
  2. Along the width: 14.5 ft ÷ 12 = 1.21, so 2 pieces of 11.5 ft: 276 sq ft.
  3. The length wins: 174 ÷ 9 = 19.33 sq yd, 13% more than the 154 sq ft (17.11 sq yd) floor.

The calculator shows: "Order 14.5 linear ft of 12 ft wide carpet: 19.33 sq yd (174 sq ft)." and "1 piece 14.5 ft long runs along the room's length, with 3 in to trim at each wall and no seams. Floor and pad: 154 sq ft (17.11 sq yd), so you order 13% more carpet than floor. Running the pieces along the width instead takes 23 linear ft (276 sq ft)."

Second example: a 12 x 12 ft room

With 3 in at each wall, the carpet must span 12.5 ft, wider than a 12 ft roll, so it takes two pieces and a seam: "Order 25 linear ft of 12 ft wide carpet: 33.33 sq yd (300 sq ft)." With the 15 ft roll: "Order 12.5 linear ft of 15 ft wide carpet: 20.83 sq yd (187.5 sq ft)." Only if your installer confirms a 12 ft piece fits with no trim, set the trim to 0: "Order 12 linear ft of 12 ft wide carpet: 16 sq yd (144 sq ft)."

Third example: a 20 x 16 ft living room

Two 12 ft pieces are needed either way, so the calculator runs them along the 16 ft width, where each is shorter: "Order 33 linear ft of 12 ft wide carpet: 44 sq yd (396 sq ft)." To run the seam along the 20 ft length, set the direction to the room length: "Order 41 linear ft of 12 ft wide carpet: 54.67 sq yd (492 sq ft)." That's 8 linear ft more.

Carpet for a 14 by 11 foot room: one 14.5 foot piece of 12 foot wide carpet, 19.33 square yardsTop view of a 14 by 11 foot room carpeted with one piece cut from a 12 foot wide roll. The piece runs the full 14 foot length with 3 inches to trim at each wall, so it is 14 plus 0.5, or 14.5 feet long, and across the room it spans the 11 foot width plus 0.5 foot of trim, 11.5 feet, which fits the 12 foot roll with 6 inches of roll width left over, so there is no seam. The pile runs the same way as the piece. 14.5 times 12 is 174 square feet; divided by 9 that is 19.33 square yards, 13 percent more than the floor, which is 154 square feet or 17.11 square yards and is also the pad area. Running the pieces along the width instead takes 2 pieces of 11.5 feet: 23 linear feet, or 276 square feet. The trim and the left-over width are drawn wider than scale.CARPET FOR A 14 × 11 FT ROOM, 12 FT ROLLRoom 14 × 11 ftfloor and pad: 154 sq ft(17.11 sq yd)piece and pile run this way14 ft room14.5 ft piece11 ftroom12 ftroll1 piece14.5 ft long off a12 ft wide roll, no seam3 in trim at each wall(0.5 ft per dimension)6 in of roll widthleft over, cut offTrim and left-over width drawn wider than scaleAcross: 11 + 0.5 = 11.5 ft, within the 12 ft roll → 1 pieceLength: 14 + 0.5 = 14.5 linear ft of 12 ft wide carpet14.5 × 12 = 174 sq ft ÷ 9 = 19.33 sq yd (floor: 154 sq ft)Along the width: 2 pieces × 11.5 ft = 23 linear ft (276 sq ft)
Each piece runs the room's full length plus 3 in of trim at each wall: 14 + 0.5 = 14.5 ft. Across, 11 + 0.5 = 11.5 ft fits one 12 ft wide piece, so there is no seam. 14.5 × 12 = 174 sq ft ÷ 9 = 19.33 sq yd, against 154 sq ft (17.11 sq yd) of floor and pad. Running the pieces along the width would take 2 pieces: 23 linear ft (276 sq ft).

Carpet by room size: 12 ft vs 15 ft roll

Square yards to order (pieces x piece length in ft) with 3 in trim at each wall, no extra, and the direction that uses less:

Room (ft)Floor (sq yd)12 ft roll15 ft roll
10 x 91012.67 (1 x 9.5)15.83 (1 x 9.5)
10 x 1011.1114 (1 x 10.5)17.5 (1 x 10.5)
12 x 1013.3316.67 (1 x 12.5)17.5 (1 x 10.5)
12 x 1114.6716.67 (1 x 12.5)19.17 (1 x 11.5)
12 x 121633.33 (2 x 12.5)20.83 (1 x 12.5)
13 x 1217.3333.33 (2 x 12.5)20.83 (1 x 12.5)
14 x 1218.6733.33 (2 x 12.5)20.83 (1 x 12.5)
15 x 122033.33 (2 x 12.5)25.83 (1 x 15.5)
14 x 1320.2236 (2 x 13.5)22.5 (1 x 13.5)
14 x 1421.7838.67 (2 x 14.5)24.17 (1 x 14.5)
16 x 1424.8938.67 (2 x 14.5)27.5 (1 x 16.5)
15 x 152541.33 (2 x 15.5)51.67 (2 x 15.5)
18 x 122433.33 (2 x 12.5)30.83 (1 x 18.5)
20 x 1533.3341.33 (2 x 15.5)51.67 (2 x 15.5)
20 x 1635.5644 (2 x 16.5)55 (2 x 16.5)
20 x 2044.4454.67 (2 x 20.5)68.33 (2 x 20.5)

Past 11 ft 6 in wide, a 12 ft roll needs a second piece. At 18 x 12, one 18.5 ft piece of 15 ft carpet still beats two 12 ft pieces; at 20 x 16, both need two pieces and the 12 ft roll wins, so wider isn't always better.

Where the seams go

Seams run the same way as the pieces, so the direction setting is also the seam direction. CRI 105 says to "Keep seams to a minimum" and, when possible, to position them so that:

  • "Seams should run the length of the area."
  • "Main traffic should run parallel to, rather than across, the seam."
  • "Natural light does not strike across the seam."
  • "Seams are away from areas subjected to pivoting traffic."
  • "Seams are not perpendicular to doorway openings."

The calculator can't see your doors, windows, or traffic paths, so set the direction yourself if its seam lands badly.

Square yards or square feet?

Home Depot's guide says "Carpet is measured in square yards. One square yard is 9 square feet," so divide square feet by 9. But Shaw lists carpet per square foot, and NIST Handbook 130's model method-of-sale rule has the seller state "The amount delivered (exact size shipped)" and use the square foot in U.S. customary units. The calculator shows both, plus linear feet. Laminate, vinyl plank, and wood floors are sold by the box instead; see the flooring calculator.

How much carpet pad do you need?

Pad area is the floor area: 154 sq ft (17.11 sq yd) in the default room. Home Depot says "The carpet pad shouldn't be placed over the tack strips," so the full floor area runs slightly high. If the subfloor under it needs replacing, the plywood calculator counts 4 x 8 sheets for the same floor.

  • Seams. Home Depot says to position the pad "so that any seams will be at right angles to the seams in the carpet." CRI 105 also allows an offset of at least 6 in.
  • Lengths. CRI 105 says to install cushion "in the longest continuous lengths possible."
  • Thickness. CRI 105: "Cushion thickness for Residential carpet installations should not exceed 7/16 inch (11 mm)."

How much extra carpet should you buy?

For plain carpet, none: the trim and the unused width of the last piece are already in the order. Home Depot's "Order 10 to 20 percent more carpet than you need" goes with its square-footage method, not on top of this layout. A percentage can also fall short: for a 12 x 12 ft room, floor plus 20% is 172.8 sq ft, but one 15 ft piece is 187.5 sq ft and two 12 ft pieces are 300.

CRI 105 says "Patterned carpet requires additional material for proper pattern matching," so ask how much the style's pattern repeat needs and enter it as extra. With 10%: "Order 15.95 linear ft of 12 ft wide carpet: 21.27 sq yd (191.4 sq ft)."

Tips and common mistakes

  • Ordering floor area ÷ 9. That's the floor, not the order.
  • A room right at 12 ft. With trim, it's wider than a 12 ft roll; try the 15 ft roll.
  • Mixing inches and decimals. 11 ft 6 in is 11.5 ft, not 11.6.
  • Forgetting that seams follow the pieces. Changing the direction moves them.
  • Skipping the seaming diagram. CRI 105 calls correct measurements and a detailed diagram essential before an installation is planned or estimated. Ask your installer for one.

Frequently asked questions

How many square yards of carpet do I need?

Floor sq ft ÷ 9 is only the floor. A 14 x 11 ft room is 17.11 sq yd of floor, but with 3 in trim at each wall it takes one 14.5 ft piece of 12 ft wide carpet: 19.33 sq yd.

How much carpet do I need for a 12x12 room?

With 3 in to trim at each wall, 33.33 sq yd off a 12 ft roll (two 12.5 ft pieces, one seam) or 20.83 sq yd off a 15 ft roll (one piece). The floor is 16 sq yd.

How wide are carpet rolls?

Shaw Floors lists 12 ft and 15 ft widths, and Home Depot sells TrafficMaster Viking 12 ft wide, cut to length. With 3 in trim at each wall, one piece covers a room up to 11 ft 6 in or 14 ft 6 in wide.

How much extra carpet should I buy?

For plain carpet, none on top of this layout: the trim and full-length pieces are already in the order. Home Depot's 10 to 20 percent goes with a floor-area estimate. Patterned carpet needs extra for matching (CRI 105).

Do I need the same amount of pad as carpet?

No. Pad covers the floor, so it's the floor area: 154 sq ft for a 14 x 11 ft room, against 174 sq ft of carpet. It stops at the tack strips.

Where should carpet seams go?

They run the way the pieces do. CRI 105 says to keep seams to a minimum and, when possible, run them the length of the area, parallel to main traffic, and not perpendicular to doorways.

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