What size art goes above a sofa, a bed, a sideboard.

Arithmetic, not opinion. Every measurement below is either a standard paper size or a calculation, and the working is shown. Check it against your own wall before you drill.

The calculation

The reference point is the furniture underneath, not the wall. The convention designers use is two-thirds of the furniture's width — and it applies to the whole arrangement, not to any one piece in it.

The arithmetic on the three-seater row, because it is the one people get wrong: three A2s hung portrait are 42 cm wide each, so 126 cm of paper. Two 7 cm gaps adds 14 cm. Total 140 cm, against a 140 cm target. That is why sets of three exist.

None of those land on the target exactly, and they don't need to. Two-thirds is a target to get near, not a figure to hit — anywhere between about 60 and 80 per cent of the furniture width looks right. What does not look right is 20 per cent.

A single A3 above a three-seater spans 30 cm against a 140 cm target — about a fifth of what the wall is asking for. That is the mistake, and it costs nothing to avoid.

Which sizes those numbers mean

Sizes from overseas sellers — 30×40, 50×70, 18×24 inches — are close to these but not the same, and the near-misses are what stop a print sitting in an off-the-shelf frame. The full conversion table and the two traps are on print sizes explained.

What the frame adds

You are not hanging the print, you are hanging the frame. A framed print with a mat is considerably bigger than the paper inside it:

• A standard mat border adds 5–7 cm on every side.
• The frame moulding adds another 2–4 cm on every side.

So an A3 print (29.7 × 42 cm) matted and framed occupies roughly 45 × 57 cm of wall. An A2 becomes about 58 × 75 cm. Plan with the framed figure, not the paper figure, or your gallery wall will not fit.

This cuts the other way too: matting is how you make a small print look intentional. An A4 in a wide-matted frame reads as a considered object. The same A4 with a thin frame and no mat reads as a certificate.

Portrait or landscape

Match the shape of the space, not the shape of the picture. A wide, low wall — above a bed head, behind a sofa, over a sideboard — wants landscape or a horizontal row of portraits. A narrow wall between two doors, or a wall with high ceilings and nothing under it, wants portrait. If you are buying a set, keep every piece in the same orientation; mixed orientations in one group need a much more confident hand than the rule of thumb can supply.

The short answer

If you want one number to carry around: most people should buy one size up from the one they were about to buy. Undersized art is the single most common complaint, and it is irreversible once the holes are in the wall.