Revealed: The five secrets to selecting your super sofa

We share advice on how to make that essential seating purchase

Some iconic sofa profiles like the pillow-style Togo are low, wide and closer to a mattress than a chair; from €3680 for a small sofa, Ligne Roset, Dublin.

If that sofa on sale is calling to you, put it through its paces for more than good looks. Sprawled akimbo by the low, melting modular after an inelegant genuflection? Nagged upright with your knees up your nose by that pert two-seater? The internal dimensions of any sofa, its overall design and the support from its frame and upholstery fill will all manipulate your body. These sly details will either deliver furniture that’s easy to get into and out of, or a moment to dread if you have any sort of physical challenge. Follow our pointers to select your sofa wisely.

Scale and placement

Broadly speaking, when buying sofas, we’re exploring two-seaters, three-seaters (with or without a return into a chaise or L-shape), cuddlers/love-seats (with enough room for two) and sectional sofas that can play chairs and couch depending on the occasion. Whatever its overall line, the guide for finding a perfect physical match to an armchair or sofa remains the same. Obviously, before tailoring the sofa to our bodies, we must determine the available space in the room. When researching the right size of sofa, most interior designers determine proportion using the two-thirds rule. The length of the sofa should be around two-thirds of the width of the room (including any side tables or floor lighting). This is a guide only, with a lot of flexibility and can be influenced by taste, and the design and dimensions of the piece.

Reserve around 40cm of shuffle space between the front edge of the sofa and any coffee table, and 80cm for traffic to be able to go behind it easily. Together with your room plan and sitting into the piece, CAD visualisers, where you can “place” individual sofas and other furnishings in the actual dimensions of your room, are a huge help here. Most suppliers will have some design tool in-store or online. The overall depth once in the room must include any chaise-end. Will it have an arm or not — will this cut across a window or radiator?

Seat width and depth

After overall sizing, seat size is a surprisingly easy area to get wrong, and it can seriously affect your enjoyment of your sofa. When ordering, don’t confuse the overall depth and the length of the sofa with the internal seating area receiving your body. A deeper armrest can seriously cut into the seat size. The width of each seat will be 40cm to 50cm. Too skinny, and you and yours will be pitched into each other. Rather than under-sizing the seating area for each person, think of slender arms or no arms to the sofa at all. In terms of height from the floor, 43cm to 45cm to the top of the base cushion is typical, but the physical experience of sitting into the couch will depend on the amount of compression allowed for by the seat fill.

Explore the depth of the seat at its narrowest point, and its relationship to the sofa back. No one wants to be bullied upright by their leisure seating. However, unsupported slouching on a very deep seat often leads to collapsing through the sofa, ending with your shoulders suckered to the upright cushion. This is a sly stressor for your back. Only your chiropractor’s six college-going kids will thank you for it. If your calves are being pried up off the floor when you sit right back on the sofa, the seat depth is too much for your frame. Too shallow a seat and upright at the back? You’ll feel like you are perched, not relaxing. Seat depths vary from 53cm to 72cm, and they should be chosen to suit you, with your legs bent at 45, roughly landing at the back of the knee at the end of the seat cushion, with your back naturally upright (but not forced) on the rear cushions.

Shallow sofas and outliers

For a very shallow sofa, think around 53cm, but with a firm set of cushions in high-density foam, it would suit a more petite person who finds rising out of a very yielding cushion and a deeper seat slightly difficult. For older users, what Americans call the “deck-height” can be closer to 50cm. When you get into the area of 62cm plus in seat depth, and 38cm off the floor, you’re more likely to lounge on the sofa, legs hinged open. These people-swallowers actively encourage us to lift our feet up. For someone short, deeper seats require a little athleticism, but the deep sofa (a short hop from a bed mattress) can offer a comfortable, enveloping place to routinely curl up, which is fine.

The Togo, from €3680 for a small sofa, Ligne Roset, Dublin.

Some iconic designs like the Togo by Michel Ducroy, with its outrageous 102cm seat depth skimming the floor, are intended as louche, low loungers. Other reclining sofas will lengthen through the seat (a great reason to SIT in anything before you buy it). In family life, it’s best to find something betwixt and between to suit a variety of positions for every adult. An additional chaise end can give you both a formal sitting solution, together with a place to throw up your legs for movie night (great in a cuddler with two long seats to fill). Powered sofa “sliders” that transform to sofa-beds can have exaggerated seat depths even when closed. Ensure you can manage their dimensions.

Sofa backs and arms

The back height of the sofa will depend on what you personally find comfortable, together with the presence of any articulated headrest (popular in Italian dandies). Higher backs, typical of classic Chesterfield, are physically present and more supportive to the back and any sofa cushions. Low-slung sofas are more popular now, and will lengthen your walls; however, matched to a rangy, wide seat cushion, they can throw you into an exaggerated spinal C-curve. Comfort must come first, last and always unless your sofa is just posing in a bit of hallway.

When seated, you should be able to rest your arm on the arm of the sofa without lifting your shoulders. The cushions are going to come into play here. How much give do the cushions have once depressed? We all love spun fibre and feather cushions. Their luxe collapse demands daily thumps, but they show off the tones and textures of materials like velvet with random crumpled planes. 

The dimensions of the sofa might seem fine, but with a very soft set of beatable cushions, you’re likely to sink down 10cm to 15cm. Firm foam has a greater formality, holding its shape, but it can feel a little stiff under the body for slinging up your feet. Adding cushions? Well, that brings us back to seat depth. Ensure you’re not pushing yourself off the couch back, closer to the seat edge.

Pivot

Keep in mind that the sofa is often the last resort for an overnight guest, so a reasonably deep seat and longer couch can be a versatile friend over the school holidays. Vast come-to-me sofas have an alluring appeal, but can the sofa be carried into the home? Remember Ross Geller’s strangled cries of “Pivot-pivot-pivot”? (Friends, NBC, season 5, episode 16). Talk these issues over with your supplier and bring the dimensions of tight halls, dog-leg stairs and twisting corridors, or you might be taking out a window on delivery. Generally, the feet can come off for transport, but it’s what is termed the diagonal-depth that will make the sofa easy or comedic to manoeuvre.