What is A4 poster size? A4 in mm, cm, inches and frames

A4 as a poster, not a page

On a desk A4 is a document, but on a wall it becomes a small poster and the design rules change. Someone walking past gives a noticeboard about three seconds. In that time they read one headline, see one picture and maybe a date. A poster at this size works when the headline is at least 60 points, the key facts sit in 20 to 28 point type and everything else is cut. The ISO 216 proportions mean an A4 poster enlarges to A3 or A2 without cropping, so a design that works at A4 can be printed bigger later if the space allows it.

Frames and mats for A4

Frame sellers list sizes in centimetres in Australia and Europe, and IKEA's range includes a 21 by 30 centimetre frame that takes an A4 sheet with a hair of overlap at the rebate. A mat, the card border inside the frame, makes a small print look deliberate; a 30 by 40 centimetre frame with a mat cut for A4 is one common way to do that. In North America frames come in inches, and an 8 by 10 inch frame crops an A4 print on every side, so either trim the poster or buy an 8.5 by 11 inch frame made for letter paper.

Paper, finish and where it hangs

For a poster that goes behind glass, 170 to 200 gsm silk or matte paper looks better than gloss because it does not mirror the room. A window poster facing the street sits in direct sun, so laminating it or printing on a heavier satin stock helps it last. A noticeboard poster held by pins needs nothing special, but leave a clear 10 millimetre border so the pins do not punch through the text. A home inkjet will print A4 posters well on photo paper, though most leave a 3 to 5 millimetre white edge.

Common mistakes

The first is treating an A4 poster like a letter and filling it with paragraphs that nobody stops to read. The second is reusing a social image of 1080 by 1350 pixels, which prints at about 130 DPI on A4 and looks soft beside crisp shop signage. The third is a frame bought in inches for a sheet measured in millimetres. The fourth is placing the event date in small type at the bottom, which is the part of a noticeboard most likely to be covered by the next poster pinned over it.

Making an A4 poster in the flyer editor

A4 portrait is one of the eight canvas sizes in the flyer editor, at 1240 by 1754 pixels, so this is a size the product makes directly. Pick A4 Portrait under Format in the generator, describe the poster, and the design comes back at that size; A4 Landscape suits a wide window display. Exports are PDF, PNG or JPG at twice the canvas, 2480 by 3508 pixels, which is A4 at 300 DPI. They are RGB with no bleed or crop marks, so for a print shop that wants bleed, keep the background colour clear of the edges or add margin with the bleed and trim calculator. The blank 2480 by 3508 PNG linked above is the same pixel size for other tools.

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