Carpet Calculator

Carpet to order = drops × roll width × (length + 6 in), drops = (width + 6 in) ÷ roll, rounded up. A 12 × 12 ft room on a 12 ft roll takes 2 drops: 33.33 yd² for 16 yd² of floor. Each room is cut in the direction that orders the least; a 15 ft roll brings the same room down to 20.83 yd².

Carpet to order

33.33 yd²

300 ft² off a 12 ft roll

Cut: 2 drops of 12.5 ft = 300 ft²
Floor area: 144 ft² (16 yd²)

Each room is cut on its own, in the direction that orders the least; leftovers are not reused.

A patterned carpet needs extra to match the pattern (Shaw): ask your retailer.

Checked October 17, 2026 by the Yardstick Math team · How we check

Worked examples

A 12 × 12 ft room on a 12 ft roll

Width with trim: 12 ft + 2 × 3 in = 12.5 ft
12.5 ÷ 12 = 1.04, rounded up: 2 drops
Each drop: 12 ft + 2 × 3 in = 12.5 ft long
2 × 12 ft × 12.5 ft = 300 ft²
300 ÷ 9 = 33.33 yd²

Result: 33.33 yd² to order for 16 yd² of floor (20.83 yd² on a 15 ft roll).

Checked by the automated test “carpet — 12 × 12 ft room, 12 ft roll, 3 in trim → 2 drops of 12.5 ft = 300 ft² = 33.33 yd²”.

An 11 × 14 ft room on a 12 ft roll

Roll across the 11 ft side: 11.5 ft with trim, so 1 drop
Drop length: 14 ft + 6 in = 14.5 ft
12 × 14.5 = 174 ft² = 19.33 yd²
The other way, 14.5 ft across needs 2 drops of 11.5 ft: 276 ft²

Result: 19.33 yd² to order, the roll laid across the 11 ft side.

Checked by the automated test “carpet — 11 × 14 ft room, 12 ft roll → 1 drop of 14.5 ft = 174 ft² = 19.33 yd², the other way 276 ft²”.

How it works

Drops = (side across the roll + 2 × trim) ÷ roll width, rounded up

Cut length = other side + 2 × trim

Carpet to order = drops × roll width × cut length, in the direction that gives the smaller figure

Square yards = square feet ÷ 9

Assumptions

Rolls are 12 ft wide, or 15 ft (Shaw Floors: “Most carpet is manufactured in 12-foot rolls, although 15-foot rolls are available as well”).
3 in of trim at each wall, the CRI 105 minimum (“allowing at least 3 inches along each wall for trimming”).
Each room is cut on its own and offcuts are not reused in another room.
No pattern match: a patterned carpet needs more, as your retailer will tell you (Shaw Floors).

Reference table

Carpet to order with 3 in of trim at each wall, square yards
Room	Floor	12 ft roll	15 ft roll
10 × 10 ft	11.11	14	17.5
11 × 14 ft	17.11	19.33	19.17
12 × 12 ft	16	33.33	20.83
12 × 15 ft	20	33.33	25.83
14 × 16 ft	24.89	38.67	27.5

Each room cut in its cheaper direction, no pattern match. The roll width decides more than the floor area.

Before you order

Measure at the widest point. Take the largest length and width of each room and sketch it: CRI 105 calls correct measurements and a detailed diagram essential before an installation is planned.
Closets and doorways. Measure them as their own room, or add them to the room they open onto.

Common mistakes

Dividing the floor area by 9 A 12 × 12 ft room is 16 yd² of floor, but cut from a 12 ft roll with trim it takes 33.33 yd²: you buy the roll width, not the floor.
Forgetting the trim CRI 105 leaves at least 3 inches along each wall for trimming: 6 in more on each side of the room, enough to need a second drop.
Ignoring the pattern Shaw Floors: with a large pattern repeat “you will need more material to account for matching the pattern”. Ask the retailer before ordering.
Seams across the walkways The cheaper direction can put a seam across a hallway or a doorway. CRI 105: “Main traffic should run parallel to, rather than across, the seam”; check where the drops meet before you order.

Frequently asked questions

How to measure for carpet?

Measure each room's length and width at the widest point, add 3 in at each wall for trimming (CRI 105), then lay the roll across the side that needs the fewest drops. Type each room on its own.

How wide is a roll of carpet?

Most carpet comes in 12 ft rolls, and some in 15 ft rolls (Shaw Floors): 3.66 m or 4.57 m.

How much carpet for a 12x12 room?

33.33 yd² (300 ft²) on a 12 ft roll: with 3 in of trim at each wall the room is 12.5 ft wide, so it takes two drops. On a 15 ft roll, 20.83 yd². One 12 ft drop covers the width only if the room is under 11 ft 6 in wide.

How much carpet do I need?

More than the floor area: an 11 × 14 ft room is 17.11 yd² of floor but 19.33 yd² cut from a 12 ft roll. Count drops of the roll width, each as long as the room plus the trim.

Sources

Formula, examples and sources checked on October 17, 2026 by the Yardstick Math team. How we check our formulas.

Plan and install: carpet — Shaw Floors, accessed Oct 17, 2026
CRI 105 Standard for Installation of Residential Carpet — Carpet and Rug Institute, accessed Oct 17, 2026