Carpet Calculator

How this is calculated

Carpet is not sold by the square foot the way tile is. It comes off a roll of FIXED WIDTH - most commonly 12 feet, sometimes 15 or 13 foot 2 - and you buy a LENGTH of that width. Everything follows from that. The number of strips is the room dimension you are covering divided by the roll width, rounded up. The linear feet is that many strips times the other room dimension, plus a waste allowance for trimming and pattern matching. ⚠️ THIS MAKES ONE EXTRA FOOT OF ROOM ENORMOUSLY EXPENSIVE. A 12 foot wide room takes one strip and wastes nothing. A 13 foot wide room takes two strips and wastes about 85 percent - you buy nearly twice the carpet for 8 percent more room. The cost does not rise smoothly with room size; it jumps at every multiple of the roll width and then falls back as the room grows into the strip you already bought. That is also why the ORIENTATION matters. Strips can run either way, and the two directions rarely cost the same. A 16 by 13 room needs two 16 foot strips one way (32 linear feet) but two 13 foot strips the other (26 linear feet) - six linear feet of 12 foot carpet saved for nothing but a decision. Both figures are shown. Orientation is not purely an arithmetic choice, though. Seams are less visible running along the direction of the main light source and along the line of traffic rather than across it, and in a hallway the carpet should run the length rather than being seamed across. Where the two considerations disagree, the seam usually wins - it is permanent and you will see it every day. Carpet is frequently priced by the SQUARE YARD, which is why that figure is shown. Nine square feet to the square yard. Not included: underlay and gripper, which are bought separately and by different measures; doorway transitions; and pattern repeat, which can add substantially to the waste on a patterned carpet because strips must be aligned. If your carpet has a repeat, ask the supplier what it costs you before ordering.

Common questions

Why does one extra foot of room cost so much?

Because carpet comes off a roll of fixed width and you buy a length of it. A 12 foot wide room takes one strip and wastes nothing. A 13 foot wide room takes two strips and wastes about 85 percent - you are buying nearly twice the carpet for 8 percent more room. Cost jumps at every multiple of the roll width and then falls back as the room grows into the strip you have already paid for, which is why carpet pricing feels so unpredictable.

Should I turn the carpet the other way?

Often, and it costs nothing to check. A 16 by 13 room needs two 16 foot strips one way and two 13 foot strips the other - 32 versus 26 linear feet, six feet of 12 foot carpet saved by a decision alone. Both figures are shown for exactly this reason. But do read the next answer before choosing on price.

Does seam direction matter?

Yes, and it usually outranks the saving. Seams are far less visible running along the direction of the main light source rather than across it, and along the line of traffic rather than perpendicular to it. In a hallway the carpet should run the length rather than being seamed across at intervals. A seam is permanent and you will see it every day, so where the cheap orientation and the good one disagree, the seam generally wins.

What roll width should I enter?

Ask your supplier before you measure anything. Twelve feet is the most common by a distance, but 15 foot and 13 foot 2 inch rolls exist and are worth knowing about - a 13 foot room that wastes 85 percent on a 12 foot roll wastes almost nothing on a 15 foot one. If your room is awkward for a 12 foot roll, it is worth asking whether a wider roll is available in the carpet you want.

What about pattern repeat?

It can add substantially to the waste and this calculator does not model it, because the repeat length varies by product. A patterned carpet needs strips aligned so the pattern matches across the seam, which means cutting each strip to a multiple of the repeat rather than to the room. Ask the supplier what the repeat costs you in linear feet before ordering - on a large repeat it is not a small number.

Is underlay included?

No. Underlay and gripper are separate purchases bought by different measures - underlay by the square yard or metre from its own roll, gripper by the linear foot around the perimeter. Neither follows the carpet's roll-width arithmetic, so work them out separately from the room dimensions rather than from the carpet figure here.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Carpet Calculator at https://www.bfcbrilliance.com/tools/carpet-calculator.

What I entered:
- Room length (ft): ___
- Room width (ft): ___
- Roll width (ft): ___
- Waste allowance (%): ___

What it calculated:
- Carpet to buy — strips across the width: ___
- — or turned 90 degrees: ___
- Strips needed (as entered): ___
- Carpet you actually buy: ___
- Room floor area: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

Where the job touches structure, gas, or electrics, tell me to check local building code and whether a permit or a licensed trade is required.

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