Estimate carpet for a room — in square feet and square yards, the way carpet is sold — with a waste factor.
sq yd = area × (1 + waste) ÷ 9
Carpet is often priced by the square yard. Add waste to the room area, then divide by 9 to convert square feet to square yards.
Rooms wider than the carpet roll (usually 12 ft) need seams — add extra for matching.
A 12 x 15 ft room is 180 square feet, or 20 square yards — carpet is traditionally priced per square yard. Add 10% waste and you'd buy about 22 square yards.
Carpet comes on rolls that are usually 12 ft wide. Because this room is exactly 12 ft in one direction, you can run the carpet without a seam. A room wider than 12 ft needs a seam, which adds waste for pattern matching and a strip for the seam itself — plan the seam away from high-traffic and sight lines.
One square yard is 9 square feet. Carpet rolls are typically 12 ft wide, which affects seam placement and waste.
Carpet is cut from a continuous roll of fixed width — most often 12 ft, sometimes 13.5 or 15 ft — so you buy a length of that roll, not loose square feet. A room narrower than the roll still consumes the full roll width: a 10-ft-wide room off a 12-ft roll wastes 2 ft across its whole length. This is why an area-only number under-orders carpet.
Rooms wider than the roll need a seam, and where it falls matters — keep it out of doorways and main traffic paths. Pile direction (the nap) must run the same way across every piece and seam, or joined sections look like different colors. That constraint can force extra waste because you cannot simply rotate a leftover to fit.
About 14.7 square yards including 10% waste.
Carpet is traditionally priced per square yard, where one square yard equals nine square feet. Convert the purchased roll area, not the bare floor area, since roll width drives the real quantity.
Estimate about 1.5 linear feet of carpet depth per step (tread plus riser), times the stair width. A waterfall versus an upholstered installation changes the amount slightly.
Yes. Carpet cushion is ordered separately by the square yard or roll, sized to the floor area rather than the roll-width purchase, along with tack strip around the perimeter and seam tape for any seams.