The most common mistake, by far, is choosing a canvas that is too small.
It looks big in a gallery, it looks big on a screen, and once hung it floats in the middle of the wall like a postage stamp. This is not a matter of taste, it is a matter of proportion — and proportions can be written down.
Here are the rules I use, and the ones the wall tool on this site follows.
Above a piece of furniture: two thirds
The proportion that almost always works: the work occupies between 55% and 75% of the width of the furniture it hangs above.
In practice, above a 220 cm sofa, aim for 120 to 165 cm wide. That can be one large canvas, or two 80 × 80 canvases with a gap — more on that below.
Below half the width of the furniture, the balance breaks: the furniture crushes the painting. Beyond three quarters, the work visually overflows and the wall looks too small for it.
And keep 10 to 15 cm between the top of the furniture and the bottom of the work. That is the detail everyone forgets: without that gap the two visually stick together, and the painting looks as though it were resting on the sideboard rather than hanging on the wall.
On a bare wall: centre at 150 cm
On an open wall the rule is simpler still: the centre of the work goes about 150 cm from the floor. That is average eye level, the height museums use, and it is the value the tool applies by default.
We almost always hang too high. A painting placed at ceiling height is no longer looked at: it is endured. With high ceilings — above 2.50 m — you can raise the centre, but far less than you would imagine.
A simple check: step back three metres and look straight ahead. Your gaze should land on the painting, not above it.
Two or three canvases: spacing is everything
A multi-work hanging depends on a single parameter: the gap between them must be constant, and smaller than the smallest of the canvases.
Allow 5 to 10 cm between two medium sizes. Beyond 15 cm the eye no longer reads them as a group, but as two paintings with nothing to say to each other.
And align what needs aligning: either the centres on one horizontal line, or the top edges. Both work; approximate does not.
Three identical sizes evenly spaced produce a calm rhythm. One large canvas with two small ones produces a composition — livelier, and harder to get right.
The sizes, in practice
40 × 40 cm — a corridor, a space between two doors, a bedroom, or in a group of three. Alone on a large wall, it disappears.
50 × 50 cm — above a console, a desk, a narrow chest of drawers. It is often the size of a first acquisition.
80 × 80 cm — the most versatile: it holds its own above a medium sofa, and it also works in pairs.
100 × 100 cm and above — a real wall, with room to step back. A large canvas needs three or four metres of distance. In a narrow room it becomes oppressive: that is the only situation where too big is genuinely a problem.
The depth of the stretcher, always overlooked
Almost all of my canvases — 96% of the current catalogue — are mounted on 3D stretchers, with deep edges of about 4 cm. That changes two things.
First, they hang without a frame: the painting stands on its own and lifts off the wall by its own thickness. That is how I sell them — works are delivered unframed.
Second, that depth casts a shadow on the wall which changes with the daylight. It is part of the painting, not a flaw in the finish.
On a few older canvases I used to continue the composition around the edges. I no longer do: the edge belongs to the object, not to the image.
The only way to be sure
All these rules are starting points. They do not replace the one check that counts: seeing the canvas on your wall, at its true size.
That is what the tool on this site does. You photograph your wall, you give one known measurement — the width of a window, the height of a door — and the canvas appears to scale. You can compare an 80 × 80 and a 100 × 100 in the same place, and decide in two minutes what a catalogue would never have settled.