What Size Rug Pad Do You Need?

The rule is short: the pad should be about 25mm smaller than the rug on every side.

It is the part people most often get wrong, usually by buying a pad the same nominal size as the rug and laying it down as it comes.

Why smaller

A pad that reaches the rug's edge holds that edge up off the floor. Three things follow, and all of them are avoidable.

A visible ridge. The rug's border sits proud of the floor rather than lying down into it. It reads as a line around the whole rug, and it looks like exactly what it is.

A trip and catch point. A raised edge catches feet, vacuum heads, chair legs and doors. On a runner in a hall this is a genuine hazard rather than an annoyance.

Edge wear. The border and selvedge are the thinnest part of a rug and the first thing to wear anyway. Holding them proud puts every passing foot directly onto them. On a hand-knotted rug that is the difference between rebinding an edge in twenty years and rebinding it in five — rug repair.

Set the pad 25mm in on each side and the rug's edge lies flat to the floor, tapering down from the pad. Nothing catches, nothing shows, and the border wears at its own pace.

Sizes to buy

Pads are sold in the same nominal sizes as rugs, so the usual approach is to buy the matching size and trim 25mm from each side.

Cutting one

Straightforward, and worth doing carefully because you only get to cut it once.

Felt. Heavy scissors or a sharp utility knife against a straight edge. Felt cuts cleanly and does not fray, so the finished edge needs nothing.

Felt with rubber backing. Cut from the felt side with a fresh blade. Expect two or three passes rather than one — forcing a blunt blade through the rubber layer tears it and leaves a ragged edge that will shed.

Pure rubber. Sharp blade, light pressure, several passes. Rubber grips a blade and drags, so slow is faster here.

The method.

1. Lay the rug face down on a clear floor.
2. Lay the pad on top of it, rubber side up.
3. Trace the rug's outline onto the pad with chalk or a marker.
4. Draw a second line about 25mm inside the first.
5. Cut on the inner line, using a straight edge for straight sections.
6. Flip the rug back over, position the pad, and lay the rug on top.

Cut slightly generously on the first pass. Trimming more off is easy; putting it back is not.

Odd shapes

The trace method above handles round, oval and irregular rugs without any measuring at all — trace the actual outline, step 25mm inside it, cut.

For a round rug, cutting a smooth curve is easier with scissors than with a knife. Small deviations do not matter; the pad is invisible.

Runners and halls

Runners are where the sizing rule matters most, because a raised edge in a corridor is walked over constantly and from both directions.

Same 25mm rule on all four sides. If the runner is being cut to length for the hall as well, cut the rug first, then the pad to the finished rug.

Joining pads for a large rug

For oversized rugs, pads are usually sold in widths that will not cover the rug in one piece.

Butt two pieces together edge to edge — do not overlap them, which creates a permanent ridge straight across the rug. If they will not stay put, join them on the underside with a strip of cloth carpet tape across the seam. Keep any seam out of the main traffic line where it will be compressed daily.

Two things people forget

Trim for radiators, vents and door thresholds. A pad covering a floor vent blocks it. A pad running under a door will eventually be caught by it — cut the pad back further at the door swing, not the rug.

Recut after a rug is washed. Rugs move slightly in a professional wash, and a rug that comes back 20mm shorter now has a pad reaching its edge. Check the fit when it returns — how often to clean.

For which pad to cut in the first place, see types of rug pad and rug pads by floor type.