Guide · For the trade
Carpet pile height: how it is measured, what the spec sheet means and which height to specify
Carpet pile height is the distance from the top of the primary backing to the top of the pile, in inches or millimeters and it is the single number that most changes how a carpet feels, wears and clears a door. Low pile is under 1/4 inch (6 mm), medium is 1/4 to 1/2 inch (6 to 13 mm), high is over 1/2 inch and shag starts around 3/4 inch (19 mm). The ADA limit on an accessible route is 1/2 inch and most doors, chair mats and stair nosings are designed around a pile of 3/8 inch or less.
This guide is for the designer or junior who has a spec sheet open and needs to know what ".375 in", "7 mm", ".290 cut" or "wire height" mean and what to write for the room. It covers the measurement, how mills report it, the bands and where each belongs, what it does to pad and door clearance and the questions clients bring in. For the broader case for low versus high, see the low pile vs high pile guide; this one is about the number.
How pile height is measured
The mill measures finished pile height on the shearing line: a gauge from the backing surface to the sheared tip of a cut pile, or to the top of the loop on a loop pile. It does not include the backing, so a 1/2-inch pile on a 1/8-inch backing is a 5/8-inch total thickness and total thickness is the number that matters at a door or a stair nosing. For a cut-and-loop or a multi-level pattern the sheet gives two or more heights and the difference between them is the depth of the pattern; a 1/8-inch difference reads as texture, 1/4 inch as sculpture.
How mills write it on the sheet
Every mill has its own convention and the junior should be able to read all of them.
| As printed | Mill convention | In inches | What it tells you |
|---|---|---|---|
| 0.30 in (7.62 mm) | Milliken, tufted nylon broadloom; most of the line is 0.30 or 0.375 in | 0.30 | Low to medium, commercial and residential loop and cut |
| .438 x .500 in | Masland, cut-and-loop patterns; two heights | 7/16 and 1/2 | A medium sculptured pile; the lower number is the loop |
| 0.2 in, 0.39 in | Prestige Mills, woven and tufted wool | 0.2, 0.39 | Low Wilton loop at 0.2; velvet cut pile at 0.39 |
| .290 Cut, .225 Rd. | Bloomsburg Carpet, Wilton wire height; Rd. is round wire (loop), Cut is cut wire | 0.29, 0.225 | Woven pile height in thousandths; a 4-wire repeat lists four |
| 7 mm, 1/4" | DMI, flatwoven and loop wool and sisal | 0.28, 0.25 | Low pile; metric from European looms |
| No pile (flat weave) | Couristan, flatwoven rugs and broadloom | Under 0.1 | Thinnest possible; needs a pad to feel like anything |
| 5 mm cut pile | emma gardner design, hand-knotted Tibetan | 0.2 | Low pile is standard on hand-knotted; 5.5 mm silk in the same rug |
| 0.5", 0.65" | hand-tufted and hand-loomed rugs | 0.5, 0.65 | Medium to high; the plush rug range |
Wire height on a woven carpet is the same measurement as pile height; the wire is what the pile is woven over and its height is the pile's height. A sheet that gives pile height in thousandths with no unit, such as ".290", is in inches.
Which pile height for which room
Low pile, under 1/4 inch: stairs, halls, entries, offices, anything commercial, any room with a rolling chair and the floor under a dining table where chairs slide. Density is easy to achieve at this height, which is why commercial loops at 1/4 inch outlast plush at 3/4. Medium pile, 1/4 to 1/2 inch: the living room, the family room, the guest room and most of a residence; this is where cut pile, textured and patterned tufted carpet and most Wiltons live. High pile, over 1/2 inch: the primary bedroom, the media room, the nursery floor and only where nothing rolls, nothing heavy sits on a small foot and no door swings over it. Shag at 3/4 inch and up is a rug product for a low-traffic room; see the shag rugs guide.
What the height does to everything else
- Pad. Standard residential cut pile at 3/8 to 1/2 inch takes a 7/16-inch 8 lb rebond; loop, Berber, Wilton and stair runners at 1/4 inch or under take a 1/4 to 3/8-inch dense pad (felt, rubber or 32 oz) so the loops do not stretch and the seams do not peak. A thick pad under a low pile is the most common mistake on a job; a 1/2-inch (12 mm) pad under a loop is too thick.
- Doors. Carpet plus pad is the stack: a 1/2-inch pile on 1/8-inch backing over a 7/16-inch pad is just over 1 inch and interior doors hung for hard floors will need trimming. Tell the installer the stack before the doors are ordered.
- Stairs. Keep pile at 3/8 inch or under on a stair so the nosing stays crisp and the runner wraps; the stairs guide has the constructions.
- Accessibility. ADA accessible routes cap pile at 1/2 inch, measured from the backing, with the carpet firmly attached and edges trimmed and fastened.
- Furniture. Anything over 1/2 inch will show leg indentations; use cups under a bed or a sofa and warn the client.
What to write on the spec
Give the pile height in inches with the construction and the density and note the total thickness if a door or a transition is involved: "Wilton loop, 100 percent wool, 0.25 in pile height, approximately 0.40 in total thickness, over 3/8 in 32 oz felt pad." The face weight guide covers the companion number.
Questions designers ask
What is the difference between a medium pile rug and a low pile rug?
A quarter inch. Low pile is under 1/4 inch and includes flatweaves, hand-knotted and most loops; medium runs 1/4 to 1/2 inch and includes hand-tufted and most cut-pile rugs. Low goes under dining tables, in halls and in layered schemes; medium is the living room and bedroom default.
Is a 1/2-inch (12 mm) carpet pad too thick?
Under a low pile or a loop, yes; it lets the carpet flex and the seams and loops fail early. Under a residential cut pile at 3/8 inch or more, a 7/16-inch pad is standard and 1/2 inch is acceptable if the mill's warranty allows it. Under a stair runner, never; use 1/4 to 3/8 inch dense.
What are the different types of carpet pile?
Cut pile (plush, Saxony, velvet, frieze, textured), loop pile (level loop, multi-level loop, Berber), cut-and-loop patterns and flatweave with no pile. Each can be made at several heights, so type and height are two separate lines on the spec. The cut pile vs loop pile guide covers the first two.
How can you tell if an existing carpet is low pile?
Press a ruler through the pile to the backing. Under 1/4 inch is low and a loop or a flatweave will almost always be. If a chair mat is not needed for a desk chair to roll, it is low pile.
What pile height is best for a bedroom?
1/2 to 5/8 inch in a dense cut pile or a hand-loomed wool. It is the one room where a high pile is walked on barefoot and sees no traffic, so softness can win. Keep it under 3/4 inch if a bench or a nightstand sits on it.
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