Carpet Calculator: How Much Carpet Do You Need? 2026

How much carpet a room needs

Carpet is bought by the square yard, but rooms are measured in feet, so the whole job is three conversions and one rounding-up. First, the net area: room length × room width. A 12 × 10 ft room is 120.00 sq ft of net area. Second, the waste: net × waste percentage, because cuts, seams, and mistakes eat carpet — 10% on a plain room, 15% or more on patterned carpet, which needs extra for the pattern to line up. At 10%, the waste is 12.00 sq ft. Third, the gross: net + waste, which is 132.00 sq ft here. Fourth, the square yards: gross / 9, because a square yard is 9 square feet — 132.00 / 9 = 14.67 sq yd (exact 14.6667). Fifth, the order: round the square yards UP to a whole square yard, because you cannot buy part of a yard — 14.67 becomes 15 sq yd. This is a QUANTITY calculator: it works out how much carpet to order, not what it costs. For the price, see the carpet cost calculator, which prices the room and the installation.

At the defaults — a 12 × 10 ft room, 10% waste, a 12-ft roll — the net area is 120.00 sq ft, the waste is 12.00 sq ft, the gross is 132.00 sq ft, the square yards are 14.67 sq yd (exact 14.6667), and the order is 15 sq yd. The cut plan is 1 strip of 12.00 ft on a 12-ft roll, which uses 144.00 sq ft of roll and leaves 24.00 sq ft over. Check the identities: 120.00 + 12.00 = 132.00, and 132.00 / 9 = 14.67 sq yd.

The cut plan: strips, linear feet, and leftover

A strip is one full-width piece of carpet cut to the room length. The number of strips is the room width divided by the roll width, rounded up: strips = ceil(W / roll width). A 10-ft-wide room on a 12-ft roll needs ceil(10 / 12) = 1 strip. A 14-ft-wide room needs ceil(14 / 12) = 2 strips, because one 12-ft strip cannot cover 14 ft — the second strip is the seam. The linear feet are the room length times the strips: 12.00 ft for one strip, 24.00 ft for two. The roll area used is the linear feet times the roll width: 12.00 × 12 = 144.00 sq ft for one strip, 24.00 × 12 = 288.00 sq ft for two. The leftover is the roll area minus the net area: 144.00 − 120.00 = 24.00 sq ft for the default room, and 288.00 − 168.00 = 120.00 sq ft for the 14-ft-wide room. The leftover is real carpet you paid for: keep it for repairs, stairs, or a closet. On a 15-ft roll, the default room still needs 1 strip of 12.00 ft, but the roll area is 12.00 × 15 = 180.00 sq ft and the leftover grows to 60.00 sq ft — a wider roll means fewer seams, but more leftover.

The worked example, line by line

Setup: room 12 × 10 ft, waste 10%, roll 12 ft.

Line 1 — the net area. 12 × 10 = 120.00 sq ft.

Line 2 — the waste. 120.00 × 10 / 100 = 12.00 sq ft.

Line 3 — the gross. 120.00 + 12.00 = 132.00 sq ft.

Line 4 — the square yards. 132.00 / 9 = 14.67 sq yd (exact 14.6667).

Line 5 — the order. Ceiling of 14.67 = 15 sq yd. Never the floor: 14 sq yd would leave the room short.

Line 6 — the strips. Ceil(10 / 12) = 1 strip.

Line 7 — the linear feet. 12 × 1 = 12.00 ft.

Line 8 — the roll area and the leftover. 12.00 × 12 = 144.00 sq ft of roll; 144.00 − 120.00 = 24.00 sq ft left over.

Reverse: for a gross of exactly 20 sq yd at W = 10 ft and 10% waste, the room length is 16.36 ft (exact 16.3636 ft); at 16.36 ft the gross is 179.96 sq ft = 19.9956 sq yd. The waste for a gross of exactly 150 sq ft at 12 × 10 ft is 25%. The strip boundary on a 12-ft roll is W = 12 ft: 1 strip at 12 ft, 2 strips over it. From 15 linear ft of a 12-ft roll at 10% waste, the largest net room is 163.64 sq ft (exact 163.6364 sq ft). A 14-ft-wide room on a 15-ft roll needs 1 strip, 12.00 ft, roll area 180.00 sq ft, leftover 12.00 sq ft.

Every branch, checked

L 15 ft, W 12 ft: net 180.00 sq ft, gross 198.00 sq ft, 22.00 sq yd, order 22 sq yd, 1 strip, 15.00 ft, roll area 180.00 sq ft, leftover 0.00 sq ft — the room is exactly one strip wide, so nothing is left over.

L 10 ft, W 10 ft: net 100.00 sq ft, gross 110.00 sq ft, 12.22 sq yd, order 13 sq yd, 1 strip, 10.00 ft, roll area 120.00 sq ft, leftover 20.00 sq ft.

Waste 5%: gross 126.00 sq ft, 14.00 sq yd, order 14 sq yd. Five points less waste saves one square yard.

Waste 15%: gross 138.00 sq ft, 15.33 sq yd, order 16 sq yd.

Waste 20%: gross 144.00 sq ft, 16.00 sq yd, order 16 sq yd.

Waste 0%: gross 120.00 sq ft, 13.33 sq yd, order 14 sq yd. Even with no waste at all, the ceiling still rounds 13.33 up to 14.

15-ft roll: strips 1, linear 12.00 ft, roll area 180.00 sq ft, leftover 60.00 sq ft. The order stays 15 sq yd — the roll width changes the cut plan, not the square yards.

W 14 ft: net 168.00 sq ft, gross 184.80 sq ft, 20.53 sq yd, order 21 sq yd, 2 strips, 24.00 ft, roll area 288.00 sq ft, leftover 120.00 sq ft.

W 13 ft: net 156.00 sq ft, gross 171.60 sq ft, 19.07 sq yd, order 20 sq yd, 2 strips, 24.00 ft, roll area 288.00 sq ft, leftover 132.00 sq ft. One foot over the roll width doubles the roll area.

Reverse — the other way round: the room length for exactly 20 sq yd gross is 16.36 ft (exact 16.3636 ft); the waste for a gross of exactly 150 sq ft is 25%; the strip boundary is W = 12 ft; the largest net room from 15 linear ft of a 12-ft roll is 163.64 sq ft (exact 163.6364 sq ft); a 14-ft-wide room on a 15-ft roll needs 1 strip and leaves 12.00 sq ft.

What the defaults assume

The model assumes a rectangular room measured wall to wall at the longest and widest points, a plain carpet with no pattern repeat, and one seam per extra strip. It assumes the waste percentage covers cuts, seams, and mistakes: 10% is the standard allowance for a plain room, 15% or more for patterned carpet, which needs extra so the pattern lines up. It does not model pattern repeats, stairs, closets, or irregular room shapes: measure those separately and add them to the net area. With a room length of 0, everything is 0.00. With a room width of 0, everything is 0.00. With waste 0%, the gross equals the net. With a 100 × 50 ft room, the net is 5,000.00 sq ft, the gross is 5,500.00 sq ft, the square yards are 611.11 sq yd, the order is 612 sq yd, the strips are 5, the linear feet are 500.00 ft, the roll area is 6,000.00 sq ft, and the leftover is 1,000.00 sq ft. Rounding convention: totals are computed from unrounded values, so rounded parts may differ by a cent from their rounded sum; the order is always the ceiling of the square yards, so 14.67 becomes 15 and 12.22 becomes 13, never the floor.

Output · formula · meaning

Who uses this

• The homeowner carpeting a 12 × 10 ft bedroom: they learn to order 15 sq yd — 14.67 sq yd needed, one 12-ft strip, 12.00 ft long — so they know the shop will cut one piece, and they check the 15-ft roll branch (leftover 60.00 sq ft) before paying for width they do not need.
• The renter measuring a 15 × 12 ft living room: they learn the gross is 198.00 sq ft and the order is 22 sq yd with zero leftover — so they know the room is exactly one strip wide, and they check the waste for 150 sq ft (25%) before ordering a round number.
• The DIYer with a 14-ft-wide room: they learn the room needs 2 strips, 24.00 ft of roll, and 288.00 sq ft of roll area — so they know there is a seam to plan, and they check the 15-ft roll reverse (1 strip, leftover 12.00 sq ft) before deciding whether the wide roll is worth it.
• The landlord ordering for a 100 × 50 ft space: they learn the order is 612 sq yd — 611.11 sq yd needed, 5 strips, 500.00 ft of roll — so they know the scale of the job, and they check the 10 × 10 ft branch (order 13 sq yd) before estimating the small rooms the same way.

Accuracy & limitations

The math is exact for the numbers you enter: net = L × W, waste = net × w / 100, gross = net + waste, square yards = gross / 9, order = the ceiling of the square yards, strips = ceil(W / roll width), linear feet = L × strips, roll area = linear feet × roll width, leftover = roll area − net. What the model cannot do is measure your real room: check the measurements, because a bay window, a fireplace, or a door swing changes the net area, and check the carpet, because patterned carpet needs extra waste for the pattern to line up. It assumes a rectangular room, a plain carpet, and one seam per extra strip. It leaves out stairs, closets, and irregular shapes — measure those separately and add them to the net area. It is a quantity calculator, not a price calculator: for the price, see the carpet cost calculator. For the flooring decision itself, see carpet vs hardwood flooring.