Poster Print Files: Pixel Dimensions, DPI, Bleed and Aspect Ratios

Poster sizes in pixels at 150 and 300 DPI

Pixels = inches × DPI. The table shows portrait orientation; swap the numbers for landscape. Sizes are the trimmed poster without bleed.

The physical sizes and what each is used for are on the standard poster sizes page. This page is about building the file.

How much resolution a poster really needs

300 DPI is the print-industry default for work held in the hand. Posters are seen from further away, and the eye cannot resolve fine detail at a distance. A person with normal (20/20) vision resolves about one arcminute, which works out to a maximum useful resolution of roughly 3438 ÷ viewing distance in inches.

That is why 150 DPI at final size is the usual minimum that large-format printers ask for, and why 300 DPI posters look no sharper on a wall. Use 300 DPI for posters up to about 18 × 24 in that people will inspect closely, and 150 DPI for larger formats. Photographs can drop further; vector text and logos stay sharp at any size.

Bleed, trim and safe area

Printers cannot print exactly to the edge of a sheet. They print on larger stock and cut it down, and the blade can wander by a millimeter or two. Three zones protect your design.

• Bleed: extend background color and images past the trim line, 0.125 in (1/8 in) on each side in the US or 3 mm in Europe. Some large-format shops ask for 0.25 to 0.5 in; their file spec wins.
• Trim line: the finished poster size, such as 24 × 36 in.
• Safe area: keep text, logos and faces at least 0.25 in (6 mm) inside the trim, and 0.5 in or more if the poster will be framed, since the frame lip covers about 1/4 in on each edge.

Aspect ratios: why a design will not fit every size

US poster sizes come in three shapes. Scaling a design between sizes with the same ratio works perfectly; scaling between different ratios forces a crop or empty bands.

• 24 × 36 to 27 × 40: scaled to 27 in wide, a 2:3 design is 40.5 in tall, so you lose 0.25 in at the top and bottom. Usually harmless.
• 24 × 36 to 18 × 24: scaled to 18 in wide, the design is 27 in tall, 3 in too long. Plan a layout that tolerates a crop, or make two versions.
• US to A-series: a 2:3 design placed on A1 leaves empty side bands totaling about 6% of the width; a 3:4 design leaves bands totaling about 6% of the height. Design for the ISO ratio from the start if the poster will print in Europe.

Camera photos are 3:2 (DSLR and mirrorless) or 4:3 (most phones), so a phone photo fits an 18 × 24 in poster without cropping and a DSLR photo fits 24 × 36 in. More on ratios in the aspect ratio guide and photo print sizes.

Setting up the file

1. Create the document at final size plus bleed, in inches or millimeters, not pixels. In Photoshop, set the resolution to 150 or 300 pixels per inch at creation; changing it later resamples the image.
2. Use real print units for type. On a poster read from 3 to 6 ft, body text should be 24 pt or more and headlines 72 pt or more; titles on conference posters often run 85 to 120 pt.
3. Check color mode. Offset printers want CMYK; many large-format inkjet shops prefer RGB because their printers have a wider gamut. Ask before converting, since bright greens and blues dull in CMYK.
4. Export a print PDF. PDF/X-1a or PDF/X-4 embeds fonts and keeps vector text sharp at any size. Include crop marks and bleed if the printer asks for them.
5. Proof at 100%. Zoom to 100% (actual pixels) and look at photos: whatever looks soft on screen at that zoom will look soft in print at close range.

For screen graphics rather than print, pixel sizes for each platform are on the social media image sizes page. The paper sizes chart covers smaller print formats.

Frequently asked questions