The most common mistake with wall art is not the art — it is the size. A good piece hung too small looks apologetic. Here are the rules of thumb that actually work.
Fill roughly two thirds of the space
A single piece should cover about 60 to 75 per cent of the usable wall width — the width of the wall, or of the furniture below it. Less than half, and it floats.
Above a sofa or bed, measure the furniture
Take the width of the sofa and aim for two thirds of it. On a standard three-seater of around 2 metres, that means roughly a 1.2 metre span — either one large piece or two of around 600mm with a gap between them. Leave 150 to 250mm between the top of the sofa back and the bottom of the frame.
Hang at eye level, not wall level
The centre of the piece should sit about 1.45 metres from the floor. People hang too high almost every time, usually because they are centring on the wall rather than on the eye. In a dining room, where everyone is seated, you can drop it a little lower.
Hallways and narrow walls
In a corridor you see art at an angle and from close range, so smaller pieces in a series work better than one large one. Square formats around 400 to 600mm, evenly spaced, give a rhythm as you walk.
When in doubt, go bigger
Almost nobody regrets a piece that is slightly too big. Plenty of people quietly regret one that is slightly too small. If you are choosing between two sizes and the wall is empty, take the larger.