Carpet is sold by the square yard
Carpet pricing still quotes in <strong>square yards (9 sq ft each)</strong> even though rolls are 12 feet wide. The calculator converts your room area to both units and applies the per-unit price — remember to add pad ($0.50–1.50/sq ft installed), tack strips and the installer's per-yard labor.
The 12-foot roll and the seam problem
Carpet rolls are 12 feet wide, so rooms wider than 12 feet need a seam. A 15×20 room lays as one 12-ft width plus a 3-ft strip seamed along the long axis — plan seams away from traffic lanes and toward the light. Direction of the pile must run the same way on every piece or the seam shows forever.