Measure the seat that remains
A row of large cushions can turn a compact sofa into a display shelf. Measure the usable seat depth with its normal back cushions in place, then sit down before adding anything decorative. Notice where your back and feet are comfortable.
The new cushion's thickness matters as much as its width. A generously filled square may push you forwards more than a flatter rectangular cushion. Product photographs rarely reveal that difference, so check dimensions and try a similar size from elsewhere in the house if you can.
Choose a role for each cushion
A small lumbar cushion can offer a different position from a large square one, though comfort is personal and it should not be treated as a prescribed support. A cushion beside the arm may be useful for leaning; one in the middle may simply be moved to the floor every evening.
Begin with the fewest cushions that serve the way people use the sofa. A pair may be enough, or a single cushion at one end may suit a two-person seat. There is no required odd number and no obligation to fill every corner.
Compare size with the sofa’s lines
Broad arms and a low back can make the same cushion look different from one placed on a narrow-framed sofa. Hold a paper outline or an existing cushion in position and look from the doorway. The aim is proportion, not a standard size copied from a larger sofa.
If the upholstery is patterned, a plain cushion may give it space. If the sofa is plain, one patterned cushion can introduce colour without reducing the available seat with several smaller objects. Keep the visual decision separate from the comfort test so that a pleasing pattern does not conceal an unsuitable shape.
Try the normal evening arrangement
Sit, lean, stand and share the sofa with the number of people who normally use it. The cushions should be easy to reposition without creating a pile elsewhere. If everybody removes them immediately, reduce the number or thickness.
Read the cover and insert care instructions before buying. A removable cover is useful only if its cleaning method suits your routine. Choose the size and construction that remain welcome during use, not just the combination that fills a photograph.
