BYTETOOLS

Carpet Calculator

Lay a room out against a 12 ft, 15 ft or 3.66 m roll to get drops, seam positions, running feet and true square yards, plus underlay, gripper and total cost.

31.11
Room floor area (sq yd)
2
Drops needed
1
Seams
14.50
Cut length per drop (ft)
29.00
Running length off the roll (ft)
38.67
Carpet area (sq yd)
24.3%
Layout waste

Both roll orientations

LayoutDropsCut length (ft)SeamsArea (sq yd)Waste
Strips run the short way — cheaper214.50138.6724.3%
Strips run the long way220.50154.6775.7%

The first drop starts at one wall and covers a full roll width; each further drop covers another roll width, and the last one is trimmed to fit. Seams land at multiples of the roll width from your starting wall — plan them away from doorways and out of the main traffic line even when it costs a little more carpet.

Underlay, gripper and cost

40.60
Carpet to order (sq yd)
31.11
Underlay (sq yd)
65.00
Gripper (ft)
$1,362.47
Total materials
$1,136.80
Carpet cost
$186.67
Underlay cost
$39.00
Gripper cost

Broadloom carpet is cut from a fixed-width roll, so the honest number is not floor area — it is drops × cut length × roll width. Drops = the room dimension across the roll divided by the roll width, rounded up; cut length = the other dimension plus your trim allowance, rounded up to whole pattern repeats. Both orientations are shown because turning the layout 90° often saves a whole drop. Pile direction should run the same way on every drop, which is why the layout is not free to rotate strip by strip. Estimates only.

What is the Carpet Calculator?

Broadloom carpet is cut from a fixed-width roll, so floor area is the wrong number to order from. The ByteTools Carpet Calculator lays your room out against the roll width you choose, works out how many drops it takes, where the seams land, and the running length off the roll — which is what you are actually charged for.

  • Roll-and-seam layout rather than a plain area figure — drops, seams and running length
  • Both roll orientations compared, with the cheaper one highlighted
  • Pattern repeat rounding on every drop, plus a per-drop trim allowance
  • Layout waste shown as a percentage of the room's floor area
  • Underlay area, gripper perimeter less doorways, and a full material cost
  • Copyable cut list; all calculations run locally in your browser

How to use the Carpet Calculator

  1. 1

    Pick feet or metres, your currency, and the roll width your supplier stocks — usually 12 ft, 15 ft or 3.66 m.

  2. 2

    Enter the room length and width, a trim allowance for each drop, and the pattern repeat (leave it at 0 for a plain carpet).

  3. 3

    Read the drops, seams, cut length per drop and square yards, and compare the two roll orientations in the table.

  4. 4

    Set the extra waste allowance, doorway count and doorway width so the gripper length skips the thresholds.

  5. 5

    Enter carpet, underlay and gripper prices to get the material total, and copy the drop-by-drop cut list.

About the Carpet Calculator

Broadloom carpet is cut from a fixed-width roll, so floor area is the wrong number to order from. The ByteTools Carpet Calculator lays your room out against the roll width you choose, works out how many drops it takes, where the seams land, and the running length off the roll — which is what you are actually charged for.

It plans both orientations and shows them side by side, because turning the layout ninety degrees often saves a whole drop. Each drop is rounded up to whole pattern repeats where a patterned carpet needs matching, and the layout waste is reported as a percentage so you can see what the roll width is costing you.

Underlay is quoted on the room area, gripper on the perimeter less the doorways, and everything is priced in the currency you pick. All of it runs in your browser with nothing uploaded — a genuinely local estimate you can take into the shop.

Frequently asked questions

How do I calculate how much carpet I need?

Divide the room dimension running across the roll by the roll width and round up — that is your number of drops. Multiply the drops by the other dimension plus a trim allowance to get the running length, then multiply by the roll width and divide by nine for square yards.

What width does carpet come in?

Broadloom is most commonly 12 feet wide in North America, with 15 feet available for wider rooms. Metric rolls are 3.66 m, 4 m or 5 m. The roll width drives everything: a 13-foot-wide room on a 12-foot roll needs two drops and wastes a lot.

Why do I need more carpet than the room's square footage?

Because carpet is cut in full-width strips from a roll, and the last strip is trimmed to fit with the offcut wasted. Pile direction has to run the same way on every strip too, so you cannot rotate pieces to nest them. Twenty percent over the floor area is normal.

Where should carpet seams go?

Away from doorways and out of the main traffic path, running the same direction as the light where possible. Seams fall at multiples of the roll width from whichever wall you start at, so choosing the starting wall is how you control where they land.

How much extra carpet do I need for a pattern repeat?

Every drop has to be cut to a whole number of repeats so the pattern lines up across the seams, which means each drop grows to the next multiple of the repeat length. On a large repeat that can add a foot or more to every single drop.

How much tack strip or gripper do I need?

The room perimeter less the width of each doorway, since gripper is not fitted across a threshold. This calculator subtracts your doorway count multiplied by the doorway width automatically.

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