The short version. Measure the wall, then buy one size up from the one that feels safe. Undersized art is the commonest mistake in this whole business and it's the one you can't fix afterwards.
The five sizes, in millimetres
Three of them are A-sizes from the international paper series, ISO 216. A4 is 210 by 297 millimetres, A3 is 297 by 420 and A2 is 420 by 594. The pattern is the point: each size is the previous one folded in half across its long side, which works only because every sheet in the series has the same proportions. That is why an A3 is exactly two A4s and why frames for all three are on every high street.
Our manufacturer’s print templates include bleed: extra image around the edges that is trimmed off during production. For the products we sell, A3 arrives as a 305 by 428 millimetre file and A2 as 428 by 602, each carrying four millimetres of bleed on every edge.
The other two are metric and not part of that series: 50 by 70 centimetres and 70 by 100 centimetres. They don't halve into the A-sizes and they're slightly squarer, which matters if you are hanging them next to an A2.
Which one a wall wants
A4 is a desk, a shelf, a narrow gap beside a door frame. It's too small to be the only thing on a wall in a normal room, and it is genuinely good in a group of three or more.
A3 is the everyday size: above a workbench, in a hallway, between two pieces of furniture. It is also the size the single-line set is designed around, because four of them in a row make a timeline without needing two and a half metres of wall.
A2 is the first size that holds a wall on its own. Above a sofa, above a bed, on the wall you see first walking into a room. It is also the point at which fine detail starts to pay for itself, so a blueprint is worth having at A2 and is a compromise below it.
50 by 70 and 70 by 100 are statement sizes for a wall with distance in front of it: a stairwell, a garage, a long room. The rule of thumb that survives contact with reality is that art above furniture wants to be roughly two thirds of the width of the thing below it, which for a two-metre sofa puts you well past A2.
If you are printing your own photograph
Resolution is checked against the exact size you order rather than in general terms. The working floor is 150 dots per inch at print size, and a size that falls meaningfully below it is refused before checkout instead of apologised for afterwards. The reason it is checked per size rather than once is that the same photograph can be comfortable at A3 and unusable at A2.
The other thing worth knowing is that the file is cropped to fit the shape you chose, so the limiting resolution is set by whichever axis has to stretch furthest. A photograph that is very wide will lose more than you expect on a portrait size. The Paint Shop page covers what makes a good upload.
Next
Size settled, the frame is the other half of the decision, and it changes how big the finished object is on the wall. The framing guide takes that on. The formats page covers everything that is not paper.
Written by Craig Fearn, Petrol & Ink. Last updated .
