Carpet Calculator

What Is the Carpet Calculator?

The Carpet Calculator estimates how much broadloom carpet a room needs. It gives the answer in the units carpet is sold in: square yards for pricing, and linear feet of roll for cutting. If you enter a price, it also gives an estimated material cost.

Carpet differs from other flooring because it comes on a roll of fixed width, most often 12 feet. The installer cuts a length from that roll. If the room is narrower than the roll, part of the width is trimmed off and wasted. If the room is wider, a second piece must be seamed alongside. Both situations affect how much you pay for, and that is why carpet estimates often look larger than the room’s area.

How the Calculator Works

The calculator multiplies the room length by the width to find the floor area. It adds your waste percentage to allow for trimming, pattern matching and fitting into doorways.

It then divides the total by 9 to convert square feet to square yards, since a square yard is 3 feet by 3 feet. To find the length to cut from the roll, it divides the total area by the roll width.

It also compares the shorter room dimension with the roll width and reports how many roll widths are needed to span the room. If the answer is more than one, a seam will be required.

The Carpet Formula

Room area = Length × Width

Area to order = Room area × (1 + Waste % ÷ 100)

Square yards = Area to order ÷ 9

Length off the roll = Area to order ÷ Roll width

Cost = Square yards × Price per square yard

Converting prices

Carpet is quoted either per square yard or per square foot. To convert a square yard price to square feet, divide by 9. A carpet at 36 dollars per square yard costs 4 dollars per square foot.

Step-by-Step Explanation

1. Measure the room at its longest and widest points, into doorways and alcoves.
2. Multiply length by width for the area in square feet.
3. Add 10 percent for waste.
4. Divide by 9 for square yards.
5. Divide the area with waste by the roll width for the length to be cut.
6. Multiply square yards by the price per square yard for the cost.

Worked Example

A bedroom measures 15 feet by 12 feet. The carpet comes on a 12 foot roll and costs 30 dollars per square yard.

• Room area: 15 × 12 = 180 square feet.
• With 10 percent waste: 198 square feet.
• Square yards: 198 ÷ 9 = 22.
• Length off the roll: 198 ÷ 12 = 16.5 feet.
• Cost: 22 × 30 = 660 dollars.

The room’s 12 foot width matches the roll exactly, so a single 16.5 foot length covers it with a few inches of trimming allowance at each end and no seam.

Now consider a living room that is 20 feet by 14 feet. The room is 2 feet wider than a 12 foot roll. The installer can cut one 20 foot length and add a 2 foot strip made from a second length, or use a 15 foot roll if the style is available in that width. In practice you may be charged for about 34 square yards instead of the 31 the area suggests, because of the extra cut.

How to Use the Calculator

1. Enter the room length and width.
2. Choose the roll width of the carpet you are considering.
3. Set a waste allowance. Ten percent suits most rooms.
4. Optionally enter the price per square yard.
5. Press Calculate.
6. Check whether a seam is needed and note the square yards.

For rooms with alcoves or an L shape, total the area with the Square Footage Calculator first. If you are comparing carpet with hard surfaces, the Flooring Calculator gives boxes of plank and the Tile Calculator counts tiles for the same room. Carpeting a staircase needs the tread and riser sizes from the Stair Calculator. If the walls are being redone before the carpet goes down, the Paint Calculator estimates gallons.

Practical Tips

• Measure into door openings. Carpet should extend to the centre of the doorway under the closed door.
• Run the carpet pile in the same direction through connected rooms. Pile direction changes how the colour looks.
• Place seams away from doorways and high-traffic paths, and run them toward the main window so light does not fall across them.
• Ask the retailer for a cut plan showing each piece and seam before you agree to a quantity.
• Budget for pad. Cushion is priced per square yard and has a large effect on comfort and carpet life.
• Check what installation includes: moving furniture, removing old carpet, stairs and transitions are often extra.
• Keep a remnant for future patch repairs.

Common Mistakes

Estimating by area alone. Roll width decides the real quantity. A 13 foot wide room needs two roll widths or a 15 foot roll.

Ignoring pattern repeat. Patterned carpet needs extra length so the pattern lines up at seams. Add one repeat per seamed piece.

Mixing square feet and square yards. Comparing a per-foot price with a per-yard price makes one carpet look nine times dearer.

Forgetting closets. A closet often needs its own piece cut in the same pile direction.

Not measuring stairs separately. Stairs use more carpet than their footprint suggests, because every riser is covered too.

Choosing pad by thickness alone. Density matters more than thickness. A dense 7/16 inch pad outperforms a soft thick one.

Carpet on Stairs

For a straight stair, add the tread depth and the riser height, plus an inch or two for the nosing wrap. Multiply by the number of steps and by the stair width. A 13 step stair with 10 inch treads and 7.5 inch risers at 3 feet wide needs about 13 × 19 inches of length, which is roughly 20.5 linear feet of a 3 foot strip, or about 7 square yards.

Roll Widths

Twelve feet is the standard residential width. Some styles come in 13 feet 6 inches and 15 feet, which can eliminate a seam in a wide room. Not every style is made in every width, so check before you plan around it. Carpet tiles avoid the issue entirely and are estimated like any other tile.

Pad and Other Materials

Carpet cushion comes in rolls 6 feet wide and is ordered in the same square yardage as the carpet, without the cutting waste. Tack strip runs around the room perimeter, and transitions are needed wherever carpet meets a hard floor. Seam tape is supplied by the installer.

Fibre and Pile Choices

Nylon is the most resilient fibre and suits stairs and family rooms. Polyester is soft and stain resistant at a lower price, though it flattens sooner under heavy traffic. Wool is durable and natural, and it costs considerably more. Olefin resists moisture and is common in basements and loop-pile berbers. Cut pile feels soft underfoot, loop pile wears well, and patterned cut-and-loop hides footprints.

Measuring Several Rooms

When the same carpet runs through adjoining rooms, the retailer will lay out all the cuts on one roll diagram. Offcuts from a narrow room can sometimes fill a closet or a hallway, which reduces the total. Hallways are usually cut along the roll so the pile runs lengthwise. Because of this nesting, the total for a whole floor is often a little less than the sum of rooms estimated individually. Use the calculator for each room to set a budget, then ask for the roll diagram to confirm the order.

Preparing for Installation

Clear small items and breakables from the room and decide who is moving the furniture. Old carpet and pad need to be lifted and disposed of, and the subfloor should be swept, with squeaks screwed down and any damaged areas repaired. Doors may need trimming if the new carpet and pad are thicker than the old. After installation, vacuum to remove loose fibres, which is normal shedding for cut-pile carpet in the first few weeks.