How the Carpet Calculator works
You can add as many rooms as the job has. The tool sums length × width across all of them for total square footage, then divides by 9 to get square yards, since carpet is sold as roll goods by the yard. Waste is applied to the yardage — 10% by default — because trim loss lands on the carpet, not on the substrate.
Padding is calculated separately at 5% over the net area rather than the carpet waste factor. Pad is cut room by room with minimal trim and no pattern matching, so it carries less loss than the carpet above it.
Trim materials come off room geometry. Tack strip is the perimeter of every room, 2 × (length + width) summed across rooms, priced at $0.50 per linear foot. Seaming tape is estimated at 12 linear feet per room. Carpet is priced at $3, $5, or $8 per square foot for builder, mid-range, or premium grade, and pad at $0.50, $0.80, or $1.20 for standard 6 lb, premium 8 lb, or memory foam.
Worked example: one 12 ft by 10 ft room is 120 square feet, or 13.33 square yards. Adding 10% waste gives 14.67 square yards of carpet, alongside 126 square feet of pad, 44 linear feet of tack strip, and 12 feet of seaming tape. In mid-range carpet at $5 per square foot with standard pad, that is $660 of carpet, $63 of pad, and $22 of tack strip — about $745 in materials.
Frequently Asked Questions
Why is carpet sold in square yards instead of square feet?
Carpet comes off a roll, historically 12 feet wide, and the trade has always priced roll goods by the yard. One square yard is 9 square feet, so you divide your square footage by 9. A 12 by 10 foot room is 120 square feet, or 13.33 square yards before waste.
How much waste should I allow on a carpet order?
Ten percent is the default and works for simple rectangular rooms. Raise it for rooms whose width does not divide neatly into the roll width, for closets and hallways coming off the same roll, and for patterned carpet, where each piece has to be shifted to line the pattern up across a seam.
Why is the pad quantity different from the carpet quantity?
Pad is estimated at 5% over the net floor area rather than the carpet waste percentage, because pad is cut to the room with far less trim loss and does not need pattern matching. A 120 square foot room takes 126 square feet of pad but 14.67 square yards of carpet.
How much tack strip and seaming tape do I need?
Tack strip runs the perimeter of every room, which the calculator computes as 2 x (length + width) per room and prices at $0.50 a linear foot. Seaming tape is estimated at 12 linear feet per room. Both are small line items, but leaving them off an estimate is a common way a flooring bid comes in short.