A rug is bought for a floor, so the floor is where the measuring starts. This page is the room's advice on sizes, on what a pad is for, on turning a piece, and on the one household machine that does more harm to a rug than feet ever do. It ends with the list of things the room will not do.
Measure the floor, not the room. Walls are not where a rug stops; the skirting, a radiator, a hearth and the swing of a door all take floor away, and the rug has to sit inside what is left. Run a tape along the two directions at floor level, write both figures down in centimetres, and note anything that intrudes.
Then decide how much floor you want to see. A rug that runs to the skirting on all sides reads as fitted carpet; a rug that stops well short of the walls reads as a rug. The band of floor showing is a matter of taste, but it should be the same on all four sides, and a hand's width is the least that reads as intentional. Take that band off both ends of each measurement and what is left is the largest rug the floor will carry.
Under a dining table the rule is different: the rug should be large enough that a chair pulled out to sit down still has all four legs on it. Measure the table, add the depth of a pulled-out chair on every side, and that is the smallest rug that works there, whatever the room around it says.
For a hallway, measure the length of floor between the two doorways or the two ends, and the width between the skirting boards. A runner stops short of both ends and leaves a band of floor along each side, and because a hand-knotted runner may not run perfectly straight, the widest point on its note is the width to plan with.
Type the floor's length and width in centimetres, and the band of floor you want to see on each side. The reckoner takes the band off both ends of each measurement and gives the largest rug that fits, in centimetres and in feet and inches. It is subtraction and a unit change, nothing more; the judgement about the band is yours.
Largest rug, length: —
Largest rug, width: —
The same in feet and inches: —
Hand-knotted pieces come in the sizes they were woven at, so the answer is a ceiling, not a target. A listing a little under it will work; a listing over it will not.
A pad does three things, and only one of them is about comfort.
It holds the rug still. On a wooden or tiled floor a rug without a pad creeps with every step and ends up somewhere it was not put, and a runner in a hallway will walk the length of the corridor in a week. A pad with grip on its underside stops that.
It keeps the edges down. A rug whose corner lifts is a rug that gets caught by a foot, and a caught corner is where a selvedge starts to fail. A pad cut a little inside the rug's own edges lets those edges lie flat on the floor.
It takes wear. Every step on a rug presses the knots against whatever is underneath. Against a hard floor the foundation takes that; against a pad it is spread, and the pile lasts longer for it. On a fitted carpet the pad is thinner and its job is mostly the first one, since a rug on carpet walks even more than a rug on boards.
Pads here are cut to a piece's own measurements, a little under on each side so the pad never shows. Ask for one with the rug and it comes in the same parcel.
A rug wears where it is walked on and fades where the sun lands, and neither happens evenly. Turning the rug end for end moves the walking line and the sunlit patch to the other half, and over the years that is the difference between a rug that has worn all over and one that has a bald path down its middle.
Turn it when the season changes, which is often enough to matter and rare enough to remember. If one end sits in a window, turn it more often than that. A runner in a hallway is turned end for end the same way, and it is worth turning it over too, face down for a day, so the back gets air.
Turning is also the moment to look. Lift a corner, look at the back for the pale line of a moth, run a hand along the selvedge for a place where the wrapping has opened. Anything found is a job for a repairer, caught early.
A vacuum cleaner with a rotating brush is the thing in a house most likely to damage a hand-knotted rug, and the fringe is where it does it. The brush catches the free warp threads, twists them, and pulls them out of the end of the rug a few at a time; a fringe that has been vacuumed for a few years is short, ragged and taking the end of the pile with it.
So: suction only, never a beater brush, and never across the fringe at all. Vacuum the field in the direction the pile lies, which you can find by running a hand across it, the smooth way. Stop the head short of the ends. Shake the fringe out by hand, or comb it with your fingers, and leave it at that.
A flatweave has no pile and can be vacuumed on either face, but its ends and its selvedges are just as easily eaten. Cushion covers are not vacuumed; they are taken outside and shaken, or aired flat in shade.
Spills are blotted, not rubbed, and never soaked, because dyes in old wool can run and the room cannot tell you which will. Anything beyond blotting is cleaning, and cleaning is not done here.
You will get back the pieces in the room that fit inside it, each with its note and photographs.