The distance that makes talking easy

You can tell when a seating group is wrong before you can say why. Either everyone is leaning in and shouting across the room, or knees are almost touching and nobody can stretch out. Both come down to one number: how far apart the people sit.

A widely repeated rule of thumb from interior designers is that seats meant for conversation should be no more than about 2.4 metres (8 feet) apart. Past that you start raising your voice, and the group splits into two quiet halves. At the other end, once people are closer than roughly 1.2 metres, a living room starts to feel crowded unless you are very close friends. That leaves a comfortable band of about 1.2 to 2.4 metres, and most cosy rooms sit inside it.

Drag the seats and see

Below is a top-down plan of a living room 480 cm wide and 360 cm deep. The sofa is 200 cm wide and sits near the bottom. Drag the two armchairs (or tap one and use the arrow keys) and watch the distance between each pair of seated people.

Why these numbers work

Conversation is about hearing each other at a normal volume and seeing faces without turning your whole body. In a quiet room, a relaxed voice carries comfortably across a couple of metres. Beyond that, people lean forward, repeat themselves or give up, and the room goes quiet in the middle.

The lower limit is about comfort rather than sound. Being closer than about a metre and a bit to someone you are not leaning on is fine for a few minutes and tiring for an evening. So the target is not "as close as possible". It is close enough to chat, with room to cross your legs.

Break the rule when the room asks you to

These are guides. A big open-plan room can hold a bigger group if you accept that one end will be a separate chat. A tiny flat may have seats closer than 1.2 metres, and that can still feel snug rather than cramped if there is a throw to share and a side table within reach. The aim is that nobody has to shout and nobody has to squeeze past knees.

Also leave a clear walkway. Keep a path of roughly 75 to 90 cm between seating and a doorway or the next piece of furniture, so the group does not turn into a wall people have to climb over.

Try this before you buy anything

You do not need new furniture to fix a stiff or sprawling room. Pull the armchairs in a little, angle them towards the sofa instead of lining them up with the wall, and see how the room feels for a week. Second-hand armchairs and swapping pieces between rooms are often all it takes.

• Measure the room in cm, wall to wall, and note where the doors and radiators are.
• Measure what you own or plan to add: width and depth of every chair and the sofa, and check the doorway and stairs it must pass through.
• Mark it out on the floor with masking tape or sheets of newspaper at real size, then sit in the spots and talk.
• Anchor tall furniture such as bookcases to the wall if it sits near the seating.

If the tape plan feels right, the real furniture will too. If it feels off, move the tape, not your wallet.