A stretch cover is forgiving, but it is not blind. It needs to know what it is fitting. The difference between a cover that hugs your sofa like it was tailored for it and a cover that bunches at the armrest is rarely the cover itself — it is the four numbers you wrote down before you ordered.
This guide walks through those four numbers, the three sofa shapes most living rooms hold, and the small details that make a stretch cover sit right the first time. Read it once before you buy. Keep a soft tape measure within reach. By the end of fifteen quiet minutes with your sofa, you will know exactly which size to choose.
Why measuring matters more than guessing the seat count
The most common way people buy a sofa cover is by counting seats. A two-seater. A three-seater. A four-seater. It feels intuitive, and most of the time it is close enough — but close enough is not the same as right. A wide three-seater from one furniture maker can be 30 cm longer than a compact three-seater from another. A sofa with thick rolled armrests fits differently than the same length sofa with thin track arms.
Stretch fabric covers this variation, but only within a range. Each size on a stretch cover is designed for a span of widths and depths. If your sofa lands inside that span, the cover fits. If it falls outside — even by a few centimetres on the wrong measurement — the cover either sags or refuses to clear the armrests.
Measuring takes ten minutes. It removes the guesswork. It also tells you, before you order, whether your sofa is one piece, two pieces, or three — which decides how many covers you actually need.
The four numbers you need
Before you start, find a soft fabric tape measure. A rigid metal one works but it will fight you on the curves of an armrest. Write the numbers down as you go — phone notes, a corner of an envelope, anywhere you will not lose them.
You will measure four things:
A — Total width. From the outer edge of one armrest to the outer edge of the other, across the back of the sofa. Not the seat cushion width. The full silhouette.
B — Seat depth. From the front edge of the seat to where the back cushion begins. This is what the cover stretches across when someone sits down.
C — Back height. From the floor to the top of the backrest. The cover needs to reach over and tuck behind.
D — Armrest height. From the floor to the top of the armrest. This is what tells you whether the cover will clear the arms or strain across them.
Two of these four — total width and back height — do the most work. Seat depth and armrest height refine the fit.
How to measure a straight sofa
A straight sofa is one continuous piece — two seats, three seats, sometimes four. It has two armrests, one backrest, and one base. Most stretch covers are sold for this shape by total width.
Stand behind the sofa. Place the tape at the outer edge of the left armrest. Pull it straight across the top of the backrest, following the line of the sofa, to the outer edge of the right armrest. That is your A measurement. Write it down in centimetres.
Then move to the front. Sit briefly, then stand and measure from the front edge of the seat cushion back to where the seat meets the backrest. That is B. Do not press the tape into the cushion — let it rest naturally on the surface.
Back height (C) goes from the floor straight up to the highest point of the backrest. Armrest height (D) goes from the floor to the top of the armrest, on the outside. Some armrests are rolled and curve outward — measure to the highest point.
With these four numbers, compare against the size chart for any stretch cover. A standard three-seater stretch cover usually fits a total width of around 180–230 cm. A two-seater sits closer to 140–180 cm. Your A measurement decides.
For most straight sofas, you can browse our stretch sofa covers collection and find a size that matches without compromise.
How to measure an L-shaped corner sofa
A corner sofa is two pieces joined at a right angle: the main seat section and the chaise (the longer extension where you stretch your legs out). Some are sold as one continuous frame, others as two modules that lock together. From a cover's point of view, they are always two surfaces.
You measure each section separately, the same way you measured the straight sofa, and you note which side the chaise sits on — left-facing or right-facing.
Stand at the corner where the two sections meet. The longer arm of the L is usually the chaise. The shorter arm is the main seat section. Decide which is which before you start measuring.
For the main seat section: measure A from the outer armrest to the inner corner (where the two sections meet). Measure B and C the same way you did for a straight sofa.
For the chaise section: measure A from the inner corner outward to the end of the chaise. The chaise usually has no armrest at the far end, so D only applies to the side that has one.
Note: is the chaise on your left when you stand facing the sofa, or on your right? This matters because a corner cover is shape-specific. A left-facing cover will not fit a right-facing sofa.
Most L-shaped sofas need a dedicated corner cover designed for two sections. The corner sofa covers collection is built around this shape, sized for the most common width spans.
How to measure a U-shaped sofa
A U-shaped sofa is three sections: two chaises (one at each end) and a central seat section. Some are a single continuous frame; most are modular. From a fitting standpoint, you measure three surfaces.
Treat each section as a straight sofa. Measure the central section first — A across the back, B for the seat depth, C for the back height. Then measure each chaise separately. Note which side they sit on and whether each chaise has an armrest at the far end.
Most U-shaped sofas need either a dedicated three-section cover or three separate covers (one for the main section, one for each chaise). The right answer depends on how the sofa is built. If your sofa is modular and the sections can be pulled apart, three covers usually fit better than one continuous cover stretched across the whole shape.
This is the moment to use the principle behind the brand: keep what you love, change how it feels. A modular sofa is built to be reconfigured. Covers should respect that.
The five mistakes that ruin a perfect measurement
Most measuring problems come from the same handful of habits. Avoid these and the cover will sit right.
Measuring the cushion instead of the frame. Cushions move. Frames do not. Always measure to the outer edges of the sofa structure, not the cushion edges.
Pressing the tape into the upholstery. Let the tape rest naturally. Stretch fabric needs to span the relaxed surface, not the compressed one.
Forgetting the armrests on width. A frequent error is measuring only the seat width — the part you sit on — and forgetting that the armrests add 15 to 30 cm on each side. A stretch cover wraps the whole silhouette.
Mixing units. Centimetres on the sofa, inches on the size chart. Pick one and stay with it. Most stretch cover size charts list both, but check before you order.
Skipping seat depth. People often measure width and back height and stop there. Seat depth decides whether the cover stretches comfortably across the cushions or strains. It matters as much as the others.
What to do if you fall between two sizes
Stretch covers are designed to fit a range, but sometimes a sofa sits exactly between two sizes — say, the upper limit of a two-seater and the lower limit of a three-seater. When that happens, size up.
A slightly larger cover will tuck more fabric behind the cushions and along the base. That extra fabric is forgiving — it can be smoothed into the gaps and tightened with foam rods or the cover's own elastic band. A slightly smaller cover stretches too tight, sags away from the armrests, and never quite settles.
When in doubt, choose the larger size. The cover is built to be tucked.
What about chaise-only sofas, sofa beds, and modular pieces?
Some sofas do not fit the three-shape model. A single chaise lounge — one armrest, a long seat, no backrest on one side — needs its own measurement: A across the full length, B for seat depth, C only on the side that has a back.
A sofa bed (one that folds out into a mattress) needs measuring in its closed position. The cover fits the daytime shape, not the bed shape. Make sure the cover allows the sofa to fold and unfold without being removed entirely each time — most stretch covers tolerate this, but the looser the cover, the easier it is.
A modular sofa — pieces that lock together but can be pulled apart — should be covered piece by piece if you want the option of rearranging it. One stretched cover across the whole shape locks the configuration in place.
A short note on fabric: what stretches and what does not
Stretch covers are built around the elasticity of the weave. A four-way stretch fabric gives in every direction — across the width, down the length, and on the diagonal. This is what lets one size cover a range of sofa widths.
The fabric itself is usually a soft-touch microfibre with elastane woven through. The microfibre side faces out, gentle to the touch, calm in the room. The elastane is the working part — it pulls the fabric snug around the corners of the sofa and holds it there.
The implication for measuring: you can be slightly off, and stretch will absorb it. You cannot be very off, and stretch will save you. Measure properly and let the fabric do its job.
Once the cover arrives: a five-step fitting
Even with perfect measurements, the first fitting matters. Here is the sequence:
- Drape it loosely. Lay the cover over the sofa without pulling. Centre the seat seam over the seat cushions.
- Anchor the back. Tuck the back edge of the cover behind the backrest cushions.
- Stretch across the seat. Pull the front of the cover down over the seat and front edge of the sofa.
- Tuck the sides into the gaps. Push the side fabric into the space between the seat cushions and the armrests. This is where the cover grips.
- Adjust the armrests. Smooth the sleeves over each armrest, pulling any slack toward the back.
If your cover comes with foam rods, push them into the gaps after step 4. They lock the fabric in place and stop it shifting when someone sits down.
For ongoing care once the cover is on, see the sofa cover care guide — washing, drying, and keeping the fit are all part of the same conversation.
The thinking behind this guide
A sofa is not just furniture. It is the piece of the room that holds the most memory — where you sat with someone on a long evening, where the dog learned to stay, where a child grew tall enough to need their own seat. Replacing it is rarely the right answer. Refreshing it almost always is.
This is what we mean when we say: refresh, don't replace. Measuring carefully is the first step. The cover is the second. Read more about how this principle shapes everything we make on our story.
Take the four numbers. Compare them to a size chart. Order the size that matches — or one up if you are between sizes. The cover will arrive. It will fit. The room will feel new.
That is the promise.
FAQ
Q1: What if my sofa has an unusual shape — like a curved back or a chaise without an armrest? A1: Measure the surfaces individually. A curved back is fitted by total length along the curve, not the straight-line distance. A chaise without an armrest at one end simply does not need a sleeve there — the cover will rest naturally at the open edge.
Q2: Do I need to remove the cushions before measuring? A2: No. Measure with the cushions in place, as they sit when you use the sofa. The cover is designed to wrap around the sofa as it is normally configured.
Q3: My sofa has a recliner mechanism. Can I still use a stretch cover? A3: Most stretch covers tolerate a reclining sofa, but the cover will move with the mechanism. Tuck the fabric loosely rather than tightly so the recliner can extend without straining the fabric.
Q4: How do I know if my corner sofa is left-facing or right-facing? A4: Stand in the room facing the sofa as you normally do. If the chaise (the longer extension) is on your left, the sofa is left-facing. If it is on your right, the sofa is right-facing. Many product listings include a small diagram to confirm.
Q5: My measurements are right at the edge of two sizes. Which one do I order? A5: Order the larger size. Extra fabric tucks into the gaps and holds. A cover that is too tight cannot give you that grip.
Q6: Can I machine wash the cover after fitting? A6: Yes — most stretch covers are designed for cool machine wash and air drying. The detailed guide to washing and refitting is in our sofa cover care guide.