3 rules to stick to when picking the perfect living room sofa, explained by an interiors editor

Pip Rich has been a design journalist for 20 years, and now edits the interiors bible Livingetc. 'The most important furniture choices we make are about our sofa,' he says. 'It's where we spend our most important time: relaxing, entertaining, eating, just being. So it's key to get it right.' These are his golden rules.

Design journalist Pip Rich, editor of interiors bible Livingetc, explains the ways designers get it right.

An interior designer I admire hugely - known for his very elegant but very comfortable schemes - once told me the perfect sofa seat depth is exactly 69cm. And he's right, and I thank him often as I sink into our 69cm couch.

It's just wide enough to sit back against the rest with your feet on the floor, it's perfect for lying down across while still with enough room for your cat or dog to nestle in and it's not so big that it takes up too much valuable floor space.

Take a tape measure and look for as close to the magical 69 as you can find.

The same interior designer voiced an opinion I'd had for a while but not quite managed to formulate, and that was that while curved sofas look elegant, chic and refined, they're terrible for watching TV on.

You can't lie across them, you can't sink into them and you can't get a comfortable position in which to binge your favourite show.

So if it's a telly sofa then go for a straight lined couch - with a plump pillow, and keep your curved sofas for rooms in which you'll entertain.