"What size should my poster be?" has two answers that are easy to mix up: the physical size on paper, and the pixel size your image file needs so the print comes out sharp. This chart covers both, for the ISO A-series used almost everywhere outside North America and the inch-based sizes used in the US.
Standard Poster Sizes: ISO A-Series
The A-series is the default in Europe, Asia, and most of the world. Each size is exactly half the next one up, which makes scaling painless.
| Size | cm | Inches | Pixels @ 150 DPI | Typical use |
|---|---|---|---|---|
| A4 | 21.0 × 29.7 | 8.3 × 11.7 | 1240 × 1754 | Small notices, flyers |
| A3 | 29.7 × 42.0 | 11.7 × 16.5 | 1754 × 2480 | Small posters, window signs |
| A2 | 42.0 × 59.4 | 16.5 × 23.4 | 2480 × 3508 | Room posters, event ads |
| A1 | 59.4 × 84.1 | 23.4 × 33.1 | 3508 × 4967 | The classic "poster" size |
| A0 | 84.1 × 118.9 | 33.1 × 46.8 | 4967 × 7022 | Conference and shop displays |
Standard Poster Sizes: US Inches
US printing shops and frame stores work in inches, and the standard frame sizes do not match ISO paper.
| Size | cm | Pixels @ 150 DPI | Typical use |
|---|---|---|---|
| 11 × 17" | 28 × 43 | 1650 × 2550 | Small posters, menus |
| 18 × 24" | 46 × 61 | 2700 × 3600 | Bedroom and dorm posters |
| 24 × 36" | 61 × 91 | 3600 × 5400 | The most common US poster size |
| 27 × 40" | 69 × 102 | 4050 × 6000 | Movie theater one-sheet |
How Many Pixels Does a Poster Need?
Pixels required = inches × DPI. The rule of thumb for posters: 150 DPI is the sweet spot, because wall posters are viewed from more than a meter away and small flaws disappear. Reserve 300 DPI for hand-held sizes like A4 and A3.
Do the math for a 24 × 36 inch poster at 150 DPI: 3600 × 5400 pixels ≈ 19 megapixels. A 12-megapixel phone photo does not reach that natively — if you enlarge it anyway, the print will look soft. The fix is to upscale the photo first, then tile it.
Check the pixel dimensions, not the file size in megabytes. A heavily compressed 6000 × 9000 JPEG can print worse than a clean 3600 × 5400 PNG.
Printing a Poster Without a Large-Format Printer
Print shops charge by size, but any home printer can produce any size on this chart: split the image into a grid of A4 or Letter pages, print them, and assemble. A 3×3 grid on A4 gives a poster of roughly 63 × 89 cm (25 × 35 inches) — between A1 and A0. The free image to poster splitter does the tiling in your browser and exports a print-ready PDF with alignment marks; the full process is in our multi-page poster printing guide.
FAQ
What is the most common poster size?
In the United States it is 24 × 36 inches (about 61 × 91 cm). In countries that use ISO paper sizes, A1 (59.4 × 84.1 cm / 23.4 × 33.1 in) plays the same role.
How many pixels do I need for a 24×36 inch poster?
About 3600 × 5400 pixels at 150 DPI (roughly 19 megapixels) — the quality standard for wall posters viewed from a distance. For 300 DPI print quality you would need 7200 × 10800 pixels.
Is 72 DPI enough for printing a poster?
No. 72 DPI is a screen resolution. Wall posters should be printed at 150 DPI or more, and hand-held sizes like A4 or A3 look best at 300 DPI.
What size is a standard movie poster?
The theatrical one-sheet is 27 × 40 inches (about 69 × 102 cm). Video-store and re-release prints sometimes vary slightly, but 27 × 40 is the size collectors frame.
Can I print a large poster at home without a large-format printer?
Yes. Split the image into a grid of A4 or Letter pages with a poster splitter tool, print the pages, and tape them together — a 3×3 grid on A4 produces a poster of roughly 63 × 89 cm.