Carpet Calculator

Work out carpet in square yards for up to three room sections, with a waste allowance and a roll-width seam check.

Draft — awaiting review. Not indexed.

Formula: Area = sum of each section’s length × width. Square yards = square feet ÷ 9, then × (1 + waste).

What this calculates

This works out how much carpet a room needs, in the unit carpet is actually sold in. That unit is the square yard, not the square foot, and the difference is a factor of nine — quoting a 168 square foot room as though it were 168 square yards would be an expensive misunderstanding. The calculator takes up to three rectangular sections, because rooms with a bay, an alcove or an L-shape are common and measuring them as one rectangle either overshoots or leaves a gap. It also checks whether the room fits the width of the roll, which decides whether the job needs a seam.

How it works

Each section is length times width in feet, and the sections add together. Dividing by nine converts square feet to square yards, since a square yard is three feet by three feet. The waste allowance is then applied. The seam check compares the widest section against the roll width you select: carpet comes off a roll of fixed width — most commonly twelve feet — and a room wider than that cannot be covered in one piece, so it needs a seam. That is a fitting decision with a cost attached, and it is much better known before ordering than discovered on the day.

Worked example

A 14 by 12 foot room is 168 square feet, which is 168 ÷ 9 = 18.67 square yards. With a 10% waste allowance you would order 20.53 square yards. The widest dimension is 12 feet, which exactly matches a standard 12 foot roll, so no seam is needed. Add an alcove of 6 by 4 feet and the area rises to 192 square feet, or 21.33 square yards, and 23.47 with waste — but the alcove’s 6 foot width still fits the roll, so it remains a single-piece job.

Common mistakes

Confusing square feet with square yards is the expensive one, and it runs in both directions — a quote in yards compared against an area in feet looks nine times cheaper than it is. Second, using a 10% waste allowance on patterned carpet: a repeating pattern has to align across the room and at any seam, and matching it can push waste to 20% or beyond. Third, measuring the room at its narrowest point. Walls are rarely parallel, so measure at the widest and let the extra fall into the waste allowance rather than discovering a shortfall mid-fit.

Common questions

How many square feet are in a square yard?

Nine. A square yard is three feet by three feet. This trips people up constantly because carpet is priced by the square yard while rooms are measured in feet.

How much extra carpet should I order?

About 10% for a plain carpet in a simple room, and 15–20% for a patterned one, since the pattern has to be matched across the room and at any seam.