A sofa's comfort is built from four things working together: the suspension beneath you, the cushion fill around you, the depth and height of the seat, and the support of the back and arms. Change any one and the whole character of the sit changes. There is no single most comfortable sofa, only the right combination for how you actually sit, and once you understand the four, you can choose yours with complete confidence.

I have watched a great many people shop for sofas, and almost everyone does the same thing: they sit down for eight polite seconds, bounce gently once, and announce a verdict. It is a hopeless test, and it is not their fault. Nobody has ever explained what they are actually feeling, so the eight-second bounce is all anyone has. Let me give you something better. Here are the four things your body is reading when you sit down, what each one does, and how to choose them, honestly, with the trade-offs included.

The first thingThe springs: what catches you

The single biggest difference between a sofa that is comfortable for two years and one that is comfortable for twenty is what sits underneath the cushions. A properly sprung seat is alive: steel springs give as you land, hold you while you stay, and recover completely the moment you stand. A seat without real suspension relies on foam alone, and foam alone has one career: it starts firm, softens, and never comes back.

Across our collection we use two systems, matched to each design's character. The Coco, the Barton and the Henrietta have a fully sprung seat base of individual steel coil springs, each coil working independently, which gives a deep, even, buoyant support whether you are perched with a book or stretched out entirely. The Felix, the Isobel and the Sophia carry serpentine springs, rows of sinuous steel through the seat, for a slightly firmer, beautifully consistent sit that suits their tailored shapes. The Henrietta goes one lovely step further: her back is fully sprung too, as her nineteenth century original was, so the sofa responds behind you as well as beneath you. You feel suspension rather than see it, which is exactly why so many sofas skip it and hope you will not notice. For about two years, you do not.

The second thingThe fill: how it greets you

If springs are the engineering, fill is the personality, and it is the most personal choice in the whole sofa. We offer four fills, and the honest way to choose between them is to decide where you sit on a single line: from sink-in softness at one end to shapely structure at the other, with a question attached about how much daily ritual you are willing to give your cushions.

Our feather-wrapped foam core is the sensible heart of the range: a supportive core in a generous jacket of 70% duck feather and 30% goose down, so you get the soft welcome of feather with a shape that largely looks after itself. The sustainable foam core version sits a touch firmer, with an Origin core made using plant-based polyols. All feather and down, as 100% duck feather or a 70/30 duck and goose down blend, is the traditional, deep, enveloping softness people write poetry about, and it asks for a daily plump in return, thirty seconds each morning, forever. And the natural latex core gives resilient structure using entirely natural materials. Four honest answers; the only wrong one is the one that does not match your nature.

The third thingThe seat: where your body actually goes

Seat depth is the number people overlook most, and it quietly decides whether a sofa suits you. A deeper seat invites you to curl, lounge and lie; a shallower one supports you upright, feet on the floor, back met by the cushions, which is what readers, knitters and anyone who likes getting out of a sofa with dignity tends to want. Seat height matters with it: a lower seat feels relaxed and enveloping, a higher one is easier to rise from. Neither is better. They are different lives.

The fourth thingThe back and arms: what holds you

The last layer is the one your shoulders and neck notice. Generous back cushions let you settle at different heights and angles through an evening; on the Coco, the wonderfully plump side cushions mean you can lie lengthways and be fully supported along your whole body, which is precisely why so many of our customers' photographs feature someone horizontal. Arm height matters more than people think too: it decides where a book rests, where a head lands during the film, and whether the corner of the sofa becomes the most contested seat in the house. It always becomes the most contested seat in the house.

Comfort by the life you live

The sofa that proves the point

If you want evidence that comfort is built rather than found, consider the Barton. The design is similar to a favourite sofa of Sophie's father, Sir Terence Conran, and for several decades it was a best seller in The Conran Shops around the world, which is not the kind of run a sofa has by accident. Sit in one and you can feel every choice this page has described, made all the way: the fully sprung seat of individual coils, the great 70cm depth, proportions so generous the sofa moonlights as a bed. It was designed by people who understood exactly what they were doing, and several decades of customers agreed.

And one last honest word. Because every one of our sofas is made to order, you choose the fill, and on many models the depth and dimensions can be tailored too. That freedom is wonderful and it can also be paralysing, so do not deliberate alone: tell us how you sit, who you share the sofa with and what 9pm looks like in your house, and we will tell you plainly which combination we would choose for you, and which we would not.

Questions, answered honestly