How this carpet calculator works
Carpet is sold by the square yard, so the whole job is floor area, plus waste, divided by nine:
square yards = area with waste ÷ 9 · 9 ft² = 1 yd²
At the defaults — a 12 × 15 ft room at 10% waste — that is 180 ft², 198 ft² with waste, or 22 square yards to order, about $660 of carpet; the full chain is in the worked example. Round up to the whole yard, because carpet comes off a roll and you can’t buy a fraction of a yard.
Rolls, seams, and the square yard
Carpet isn’t tile — it comes off a wide roll, and how the roll fits the room decides the real waste:
- The square yard: nine square feet. A per-foot price × 9 is the per-yard price, so you can compare quotes.
- Roll width: most broadloom is 12 ft wide; some is 13 ft 2 in or 15 ft. It sets where seams fall.
- Seams: a room wider than the roll needs a seam and a second piece — plan the seam away from the door and the light.
- Nap direction: all pieces must lay the same way or the seam shows as a shade line — that eats material.
- The pad underneath: a separate order, priced per yard too — measure it from the same area.
Carpet grades, pad, and what to spend
The number you plug in for price carries the whole budget. What separates the grades:
- Builder grade: $15–25 a yard — thin, for rentals and low-traffic rooms.
- Mid grade: $25–40 — the common bedroom and living-room choice, nylon or PET.
- Premium / wool: $40–120 — dense, durable, and the plushest underfoot.
- Pad: $3–6 a yard — don’t skimp; the pad sets how the carpet feels and how long it lasts.
- Stairs: figure extra — each tread and riser wraps material and adds waste and labor.
A last word on where to spend: put a little of the budget into the pad. A better cushion — 6 to 8 lb rebond under most residential carpet — is what makes a mid-grade carpet feel plush underfoot and last years longer, and it costs a fraction of stepping the carpet up a grade. It is the cheapest upgrade in the room, and the one you feel every day.
Carpet by room size, and grade pricing
Table 1 runs common rooms to the square yards to order at 10% waste; Table 2 is the price range by grade.
| Room | Floor | Order |
|---|---|---|
| 10 × 12 | 120 ft² | 15 yd² |
| 12 × 12 | 144 ft² | 18 yd² |
| 12 × 15 | 180 ft² | 22 yd² |
| 15 × 20 | 300 ft² | 37 yd² |
| 20 × 20 | 400 ft² | 49 yd² |
| Grade | $/yd² |
|---|---|
| Builder | $15–25 |
| Mid grade | $25–40 |
| Premium | $40–70 |
| Wool | $60–120 |
How to measure a room for carpet
- Measure length and width to the widest points, including closets and doorway recesses.
- Break an L-shaped room into rectangles and total them on the square footage calculator.
- Add 10% waste for a simple room — more for stairs, halls or a pattern.
- Read the square yards and confirm the roll width covers the room without an awkward seam.
- Order the pad and figure stairs separately from the exclusions below.
Worked example: a 12 × 15 ft room
The default, worked line by line — a 12 × 15 ft bedroom at 10% waste, $30 a yard:
with waste = 180 × 1.10 = 198 ft²
yards = 198 ÷ 9 = 22 yd²
cost = 22 × $30 = $660
Notice the room is exactly 12 ft on one side — the roll width — so it takes one width with no seam, and the waste is almost all trim. Widen it to 14 ft and you cross the roll width: now a second piece and a seam come in, the offcut is waste, and the honest waste figure climbs past 10%. That is the moment to set the waste higher, not lower.
What this carpet estimate doesn’t include
The square yards are the carpet; a finished floor is a few more lines:
- Pad. A separate order by the yard — the cushion under the carpet.
- Tack strip and seam tape. The perimeter strip and the tape under every seam.
- Labor. Stretch-in installation, stairs, and moving furniture.
- Transitions. Thresholds and metal edging at doors and floor changes.
- Old-floor removal. Tearing out and hauling the existing carpet and pad.
Carpet FAQ
How do I calculate how much carpet I need?
Find the floor area, add waste, then divide by 9 to convert square feet to the square yards carpet is sold by. A 12 × 15 ft room is 180 ft²; with 10% waste that is 198 ft², or 22 square yards. Round up to the whole yard, because carpet is cut from a roll and you cannot buy a fraction.
How many square yards of carpet for a 12x15 room?
About 22 square yards. A 12 × 15 ft room is 180 ft²; add 10% for waste and trimming to get 198 ft², then divide by 9 (there are 9 ft² in a square yard) for 22 yd². At $30 a yard that is roughly $660 for the carpet itself, before pad and labor.
How much carpet do I need for a 12x12 room?
About 18 square yards. A 12 × 12 ft room is 144 ft²; with 10% waste that is 158.4 ft², which is 17.6 square yards — rounded up to 18. The extra half-yard is normal: you round up to the whole yard and the offcut covers a closet threshold or a patch.
Why is carpet sold by the square yard?
Broadloom carpet has always been woven and rolled in yard-wide history and sold off the roll, so the trade prices it per square yard — 9 square feet. Many retailers now also quote per square foot; multiply a per-foot price by 9 to compare it to a per-yard price, or the calculator will if you enter the yard price.
How much waste should I add for carpet?
About 10% for a simple rectangular room. Add more — 15% or higher — for stairs, long hallways, L-shaped rooms, or a bold pattern that has to match across seams. The waste also covers the fact that a room wider than the roll needs a seam, which throws away the offcut strip.
How wide does carpet come?
Most broadloom comes on 12 ft wide rolls; some styles also come 13 ft 2 in or 15 ft. A room narrower than the roll takes one width with no seam. A room wider than 12 ft needs a seam and a second piece, and the leftover strip is waste — which is why wide rooms carry more waste than the floor area alone suggests.
How much does carpet cost per square yard?
Builder-grade runs roughly $15–25 a square yard, mid-grade $25–40, premium and wool $40–120. That is the carpet only; installed you also pay for pad (about $3–6 a yard), tack strip and labor, so the finished price is often half again the carpet price or more.
Sources and standards
The conversion is exact; the grades and waste are trade practice:
- Area conversion: 9 ft² per square yard — exact.
- Broadloom widths: 12 ft standard, with 13 ft 2 in and 15 ft styles.
- Waste practice: ~10% simple rooms, higher for stairs, halls and patterns.
- Round up: carpet is cut from a roll — order the whole yard, and buy one dye lot.
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