24x36 poster size: cm, pixels and the 2:3 ratio

Large poster, Arch D and the 2 to 3 ratio

Papersizes.org lists 24 by 36 inches as the US large poster and as Arch D in the architectural series, which uses 4 to 3 and 3 to 2 proportions close to screens and photographs. The 2 to 3 ratio also matches a 35 millimetre camera frame, so a photograph fills a 24x36 print with no crop. An A series design does not: A1 is 1 to 1.414, so A1 artwork enlarged to the 24 inch width ends near 34 inches, leaving a strip of about 2 inches top or bottom, or it fills the height and loses an inch and a half off each side.

Resolution for a poster this big

A 24x36 poster is read from one to three metres, so it does not need the 300 DPI of a flyer. At 150 DPI, 3600 by 5400 pixels, text and charts look clean from a step back. At 300 DPI the file becomes 7200 by 10800 pixels, nearly 78 million pixels, which slows design tools without a visible gain at viewing distance. Photographs taken on a modern phone are often 4000 pixels on the long side, enough for about 110 DPI across the 36 inch height.

Frames, tubes and boards

Ready made 24 by 36 inch frames are sold widely in the United States because it is the standard large poster size. Outside North America frame shops list 61 by 91 centimetres, which takes a 24x36 print. For a conference, check the board size the organiser gives; when the stated maximum is 36 by 48 or 48 by 36 inches, the sizes compared on the A0 page linked below, a 24 by 36 print will look small beside its neighbours. A cardboard tube of about 26 inches carries the print rolled without creasing the corners.

Common mistakes

The first is exporting an A1 or A0 file and asking for a 24x36 print without saying whether to crop or pad. The second is setting body text for a flyer, 10 or 12 points, on a poster read from two metres away; 24 points is a more realistic minimum. The third is a 72 DPI file of 1728 by 2592 pixels, which looks sharp on a laptop and soft on the wall. The fourth is a dark full bleed background on an inkjet poster, which can band and take hours to dry on cheaper paper.

Getting a 24x36 from the poster tab

The poster tab in the flyer editor makes A0 portrait and A0 landscape boards only, at 1656 by 2340 pixels, and there is no 24 by 36 inch canvas or custom size. The A0 export is 3312 by 4680 pixels; printed 24 inches wide, that is about 138 DPI, and the height comes out near 33.9 inches, so a 24x36 sheet keeps a band of about 2.1 inches that the printer can leave white or fill with the background colour. The print scale calculator shows the numbers for any target size, and the blank PNG above is 7200 by 10800 pixels, a 24x36 canvas at 300 DPI, for anyone building at the exact size elsewhere.

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