Poster sizes and frames: which size to print your poster

Choose the shape before the size

Every poster size belongs to a family with the same shape, and frames come in those families. A print in the wrong shape for its frame is either cropped or left with a strip of empty paper, so start with the frame you want and pick the print that matches it.

Our art pack has a print file for each of these four shapes, so whatever frame you buy, one of the files fits it exactly. How a day of flights becomes a print explains what is in it.

The A sizes

Outside North America most frames follow the international A sizes, set by the ISO 216 standard. Every A size has the same shape, with the long side about 1.41 times the short side, and each one is half the area of the size above it:

The 50×70 cm frame, common in European shops, is so close to the A shape that an A-size print fits it with only a few millimetres to trim.

18×24 in, A2 and 45×60 cm are not the same

These three sit on the same shelf in a frame shop and are easy to mix up. 18×24 in and 45×60 cm are both 3:4, so a 3:4 print fits either. A2 is narrower for its height: a 3:4 print in an A2 frame loses a strip down each side, and an A2 print in an 18×24 frame leaves a gap. Check the shape on the frame's label, not just its rough size.

How big can a print go?

A printer needs enough pixels for the size. The usual aim for a print you hold in your hand is 300 dots per inch (dpi); a poster is seen from further away, so around 150 to 200 dpi still looks sharp on a wall.

Our print files are 6,000 pixels on their long side. That is how sharp they are at common sizes:

Up to 60×90 cm they print sharp. Beyond that, a large print can still look good from across a room, but ask your print shop first.

Mounts, paper and printing

Mounts. If your frame has a mount (a mat), the print goes behind the mount's window, not the frame. Print the size of the window plus a few millimetres all round, and use the file whose shape matches the window.

Paper. A dark poster shows its paper. Gloss makes black look deep but catches every reflection; matte has no glare, and lustre (semi-gloss) sits between. For a poster on a wall that faces a window, matte or lustre is the safer choice.

Colour. A screen glows and paper doesn't, so a print looks a little darker than the same picture on your phone. Photo labs that print on photo paper keep the colours closest to the file; if you can, ask for a small test print first.

Where to print. A home printer can manage A4 or A3. For larger sizes, a local photo lab or print shop, or an online print service that takes uploads, prints on better paper. When you upload, choose the option that fits the whole picture to the paper rather than filling it, so nothing is cropped.

Phone and desktop

The pack also has a wallpaper for a phone, sized for every iPhone and most Android phones, and one for a desktop at 5K, which fits 4K displays, MacBooks and 4K TVs. They need no printing: set them as your background and the day is on your screen.