Guide · For the trade
Rug pad thickness: what the number means and which one to specify
Rug pad thickness runs from 1/8 inch to 1/2 inch, and the right number follows the rug, not the room: 1/4 inch felt-and-rubber under a hand-knotted, hand-tufted or bound wool rug; 1/8 inch rubber under a flatweave, kilim or dhurrie; 3/8 inch felt under a thin rug that needs more cushion on a hard floor; 1/2 inch only under a heavy hand-made rug in a bedroom. Under wall-to-wall carpet the standard is different: 7/16 inch 8 lb rebond for residential cut pile, and 1/4 to 3/8 inch dense pad under Berber, loop, Wilton and stair runners.
This is the specs guide, for the designer or junior reading a pad spec sheet and deciding what to write on the order: what thickness and density mean, the numbers by rug construction, what a thin rug pad is for, and what changes under wall-to-wall.
What the thickness number measures, and what it does not
Thickness is the nominal height of the pad as made, uncompressed. It tells you how much the pad lifts the rug and roughly how much cushion the client will feel. It does not tell you how long the pad holds that height. That is density, stated in ounces per square yard for felt (40 oz is the trade standard) and in pounds per cubic foot for rebond (6 lb and 8 lb are the common grades). Two pads can both read 1/4 inch and behave very differently: a 20 oz felt crushes in a year under a dining table; a 40 oz felt does not. Write both numbers on the spec. The third element is the rubber: a felt-and-rubber pad is felt on top for cushion and natural rubber below for grip, and a pure rubber pad with no felt is the thin rug pad.
How thick should a rug pad be, by construction
| Rug | Pad | Thickness | Why |
|---|---|---|---|
| Hand-knotted wool, wool and silk | Felt and rubber, 40 oz felt | 1/4 in | Cushions the knots, holds the rug flat, keeps the pile from grinding on the floor |
| Hand-tufted, hand-loomed, bound broadloom | Felt and rubber | 1/4 in (3/8 in on a stone floor) | Supports the latex backing so it does not crack with foot traffic |
| Flatweave, kilim, dhurrie, sisal | Rubber, or a thin felt and rubber | 1/8 in | A thick pad under a flat rug makes the edges curl and the rug walk; the thin pad is for grip only |
| Rug on top of carpet | Dense rubber or a carpet-to-carpet pad | 1/8 in | Stops the rug creeping on the pile; no cushion is needed, the carpet provides it |
| Heavy hand-made rug in a bedroom | Felt and rubber | 3/8 to 1/2 in | Barefoot room, no doors swinging over it, cushion is the point |
| Runner in a hall | Felt and rubber or rubber | 1/8 to 1/4 in | A thick pad under a narrow rug reads as a speed bump; keep it low |
The one rule under all of this: the pad is cut 1 inch inside the rug on all sides, so the edge tapers to the floor and nobody catches a toe on it. For a 9x12 that means a pad of about 8 ft 10 in by 11 ft 10 in. Any pad is trimmed on site with a utility knife; order the next size up and have the installer cut it.
The 1/4 inch rug pad: why it is the default
A 1/4 inch felt-and-rubber pad is the answer to most rug questions for three reasons. It is thick enough to protect a hand-made rug from the floor, thin enough that an interior door clears it (most doors are hung with 1/2 to 3/4 inch under them), and the rubber keeps the rug where the installer put it. On hardwood and engineered floors, specify natural rubber, not PVC; the plasticizers in cheap pads mark polyurethane finishes. The felt rug pad for hardwood floors guide covers the floor finish side.
When to specify a thin rug pad
Thin means 1/8 inch or under. Under a flatweave or a sisal the rug has no pile to protect, so the pad's only job is grip. In a doorway, the thin pad keeps the door swinging. On wall-to-wall carpet, the thin pad is the only kind that works; a felt pad on carpet makes the top rug float and wrinkle. On a stair, under a dining table and under a desk chair, the thinner, denser pad is always the one; cushion makes chair legs rock and casters bog down.
Standard carpet pad thickness under wall-to-wall
The numbers change under broadloom because the pad is protecting the carpet backing from the subfloor across a whole room. Residential cut pile takes a 7/16 inch 8 lb rebond pad; that is the thickness most mill warranties are written around, and thicker than 1/2 inch voids many of them. Berber, loop, Wilton and patterned carpet take a firmer, thinner pad, 1/4 to 3/8 inch, dense felt, rubber or a 32 oz synthetic, because a soft thick pad lets the loops flex and the backing break. Stairs take the same dense pad, cut tread by tread, which the carpet pad for stairs guide covers. A 6 lb rebond is a builder grade; specify 8 lb and the installer will not swap it.
What to write on the spec
- Pad type: felt and rubber, rubber, or rebond, with the fiber or foam named.
- Thickness in inches, and density: 40 oz for felt, 8 lb for rebond.
- Size: rug size minus 2 inches in each direction, or "cut on site 1 inch inside the rug edge".
- Floor: hardwood, LVP, stone or carpet, so the installer confirms the rubber is safe for the finish.
- Any door or threshold the rug crosses, so the finished height is checked before the rug is laid.
Questions designers ask
What is the standard carpet pad thickness?
Under residential cut pile, 7/16 inch at 8 lb density. Under Berber, loop, Wilton and stairs, 1/4 to 3/8 inch and dense. Under area rugs the standard is 1/4 inch felt and rubber, with 1/8 inch rubber under flatweaves. Thicker is not better; most carpet warranties cap the pad at 1/2 inch.
The client's carpet is 20 years old; is it a health concern?
Not by age alone, but a 20-year-old carpet and pad have collected two decades of dust and the pad has usually crumbled, which shows up as powder at the edges and a carpet that feels thin. When a room is being redone, replace the pad with the carpet; a new carpet over a flattened old pad wears out early and the mill will not warrant it.
What size rug pad for a 6x9 rug?
A pad about 5 ft 10 in by 8 ft 10 in, which is 1 inch inside the rug on all sides. Order a 6x9 pad and have the installer trim it, or specify a cut-to-size pad from the start. The same math gives 7 ft 10 in by 9 ft 10 in for an 8x10 and 8 ft 10 in by 11 ft 10 in for a 9x12.
Is 6 lb carpet padding good enough?
It meets the minimum for residential cut pile, but it is a builder grade. For a client's project specify 8 lb rebond at 7/16 inch; the cost difference across a house is small and the carpet lasts noticeably longer on it. Under loop, Wilton or stairs, 6 lb rebond is wrong at any thickness.
Browse: felt rug pads for hardwood · carpet pad for stairs · moisture barrier carpet pad · rug on carpet · all rugs