gizmobench

Carpet Calculator

A square yard figure for the floor is not the order. Carpet comes off a roll of a fixed width, it is sold by the full width of that roll, and the moment a room is wider than the roll there is a seam and an offcut. Here the roll width is an input, the strips are laid out both ways round so you can see which direction buys less, and the run, the seams, the offcut and the waste are four separate numbers rather than one padded total. A pattern repeat cuts every strip to a whole number of repeats, which is the part that makes a patterned carpet cost more than its area suggests.

Room not measured yetRoll 12 ftPattern noneAllowance 0%

Type the room width and length below. The strips, the seams between them and the length to order off the roll appear here.

A 12 by 15 ft room on a 12 ft roll is one 15 ft run with no seam. A 13 ft room on the same roll is two runs and a seam.

Room area
0 sq ft
Carpet, sq yd
0
Roll runs
0
Waste
0 sq ft
Length to buy
0
Seams
0

The room

One rectangle, measured wall to wall at the widest point. Feet and inches are read as written, so 12' 6" is fine, and so is 12.5.

Measured in

The roll and the strips

The roll width decides the whole order. Best fit lays the strips both ways round and keeps the one that buys less; fix the direction yourself when the pile has to run a particular way.

Roll measured in
Widths carpet is sold in
Strip direction
Repeat measured in

Allowance and price

The waste figure above is already the real difference between the roll and the floor, offcut included, so the allowance starts at zero. Add a few percent for trimming and out-of-square walls if you want it.

Priced per

Worked examples

Each one runs through the same function as your own numbers. Load one to see it in the fields.

  • 12 by 15 ft, 12 ft rollone run, no seam
    15 ft of roll, 1 run, no seam, 20 sq yd
  • 13 ft wide roomsame 12 ft roll
    26 ft of roll, 2 runs, 1 seam, 34.67 sq yd
  • Pattern repeat 18"the same 13 ft room
    27 ft of roll, 2 runs, 1 seam, 36 sq yd
Quantity and layout, not fitting. Exact arithmetic on the room and roll you enter. It assumes rectangular rooms and straight runs; it does not plan seam placement for you. It counts the carpet an order needs and stops there: nothing here specifies underlay, gripper or a subfloor.

Common questions

How many square yards of carpet do I need for a 12 by 15 ft room?
The floor is 180 sq ft, which is 20 sq yd. On a 12 ft roll that is also the order: the 12 ft side lies across the roll, so one strip 15 ft long covers the room, there is no seam and there is no waste. A 13 by 14 ft room has only 2 sq ft more floor, but neither side fits a 12 ft roll, so it takes two strips, one seam and 312 sq ft of carpet. That is why the area on its own never settles the question.
Why does a 13 ft wide room need so much more carpet than a 12 ft one?
Because 13 ft will not come out of a 12 ft roll in one piece. Laid the cheaper way round, a 13 by 15 ft room takes two strips 13 ft long, so 26 linear ft of roll; laid the other way it takes two 15 ft strips, which is 30. Either way you buy the full 12 ft width, so the order is 312 sq ft, about 34.67 sq yd, for a 195 sq ft floor: one seam and a strip 9 ft wide left over, 117 sq ft of it counted as waste. Put the same room on a 15 ft roll and it takes 13 linear ft, one piece, no seam and no waste. That is the whole argument for checking the roll width before the price.
What widths does carpet come in?
Broadloom is usually 12 ft, 13 ft 6 in or 15 ft where carpet is sold in feet, and 4 m or 5 m where it is sold in metric widths. The buttons on the page set those five, and the field takes any width from 6 in to 30 ft, because runners, remnants and roll ends are not standard. The room and the roll each have their own unit, so a room measured in metres can sit on a roll quoted in feet, and a tape measure reading like 12' 6" is read as written.
How much waste should I allow on top?
Look at the waste figure the layout already gives you first. It is the real difference between what comes off the roll and what covers the floor, including the offcut beside the last strip, so it is not a percentage anyone invented. The allowance field opens at zero for that reason and adds nothing unless you ask it to. Fitters commonly add about 5 percent on top for trimming, for walls that are not square and for carpet turned into a doorway, and whatever you type is added to the run and shown in the total.
What does a pattern repeat do to the order?
It rounds every strip up to a whole number of repeats so the design can be lined up at each seam. On the 13 by 15 ft room above, an 18 in repeat turns each 13 ft strip into 13.5 ft, so 26 linear ft becomes 27 linear ft. A repeat that divides the strip exactly adds nothing. The page allows the length; it does not place the pattern, and matching it across a seam is still the fitter's work.
Can it do an L-shaped room, a closet or stairs?
No. This is a straight-strip layout for one rectangle: measure each rectangle of an L-shape on its own and add the runs together, and treat stairs as their own job, since they are cut across the roll rather than along it. It does not nest offcuts either, so a piece a fitter could use in a hallway still counts as waste here.
Does the cost figure include fitting?
No. The price you type is applied to the carpet only, on whichever basis you pick: square yard, square foot, square metre, or the linear foot or metre of roll. The result is the carpet alone and says so: it does not include underlay, gripper, fitting, delivery or tax, because those are quoted separately and vary far more than the carpet does.

Exact arithmetic on the room and roll you enter. It assumes rectangular rooms and straight runs; it does not plan seam placement for you.