# Poster sizes: A4, A3, 18 x 24 and pixels at 300 dpi

[Canonical HTML page](https://gradiently.design/guide/poster-size-guide)

Every common poster size with the pixel dimensions you need to design it, which one suits a window, a wall or a gig, and what to do when the file gets very large.

## The short version

- The most common poster sizes are A4, A3 and A2 in most of the world and 11 × 17, 18 × 24 and 24 × 36 inches in the US and Canada.
- At 300 dpi, an A4 poster is 2480 × 3508 pixels, an A3 poster is 3508 × 4961 pixels and an 18 × 24 inch poster is 5400 × 7200 pixels.
- To find the pixel size of any poster, multiply its width and height in inches by the print resolution.
- The A sizes all share the same proportions, so a design made for A4 scales to A3 or A2 without cropping.
- Posters seen from several metres away are often printed from files at 150 dpi, which halves the pixel dimensions.

The standard **poster sizes** are A4 (210 × 297 mm), A3 (297 × 420 mm) and A2 (420 × 594 mm) in most countries, and 11 × 17, 18 × 24 and 24 × 36 inches in North America. To design one for print, work at 300 dpi: an A4 poster is 2480 × 3508 pixels, A3 is 3508 × 4961 and an 18 × 24 inch poster is 5400 × 7200. The table below lists every common size, and the sections after it explain which to choose and how to handle the very large ones.

## Standard poster sizes in pixels at 300 dpi

| Poster | Millimetres | Inches | Pixels at 300 dpi |
| --- | --- | --- | --- |
| A4 | 210 × 297 | 8.3 × 11.7 | 2480 × 3508 |
| US Letter | 216 × 279 | 8.5 × 11 | 2550 × 3300 |
| A3 | 297 × 420 | 11.7 × 16.5 | 3508 × 4961 |
| Tabloid | 279 × 432 | 11 × 17 | 3300 × 5100 |
| A2 | 420 × 594 | 16.5 × 23.4 | 4961 × 7016 |
| 18 × 24 in | 457 × 610 | 18 × 24 | 5400 × 7200 |
| A1 | 594 × 841 | 23.4 × 33.1 | 7016 × 9933 |
| 24 × 36 in | 610 × 914 | 24 × 36 | 7200 × 10800 |

Trim sizes, portrait. Add the printer's bleed on every edge before you export; see [print bleed and safe margins](https://gradiently.design/guide/bleed-and-margins).

- A4: 210 × 297
- A3: 297 × 420
- A2: 420 × 594
- 18 × 24 in: 457 × 610
- 24 × 36 in: 610 × 914

Five posters drawn to scale. Each A size is exactly twice the area of the one before it; 18 × 24 is a squarer 3:4 shape and 24 × 36 a taller 2:3.

## How to work out a poster's size in pixels

Pixels equal inches multiplied by dots per inch. For a size given in millimetres, divide by 25.4 first. So an A3 sheet is 297 mm wide: 297 ÷ 25.4 = 11.69 inches, and 11.69 × 300 = 3508 pixels. The same sum gives the height of 4961. Our explainer on [DPI vs PPI](https://gradiently.design/guide/dpi-vs-ppi) covers why print shops talk about dpi when they mean pixels per inch.

```text
pixels = (millimetres / 25.4) x dpi

A3 width:   297 / 25.4 x 300 = 3508 px
A3 height:  420 / 25.4 x 300 = 4961 px

18 x 24 in at 300 dpi = 5400 x 7200 px
18 x 24 in at 150 dpi = 2700 x 3600 px
```

The whole calculation. Round to the nearest whole pixel.

## Which poster size to choose

- **A4 or US Letter** for noticeboards, staff rooms, lifts and anywhere people stand close. It is also what most office printers can handle.
- **A3 or 11 × 17** for shop windows, café walls and gig listings. It is the default size for most event posters.
- **A2 or 18 × 24** when the poster has to compete across a room or a street. Headlines can be large enough to read from several metres.
- **A1 or 24 × 36** for film posters, exhibitions, trade stands and framed prints. These are printed by a print shop, not at home.

Check the frame or the space before you start. Ready made frames in the UK and Europe are sold in A sizes; in the US they come in inch sizes such as 18 × 24 and 24 × 36. An A2 print will not sit neatly in an 18 × 24 frame, and the shapes differ enough that you can't simply scale one to the other.

An A3 event poster for a late night museum opening with a large headline and small details on a gradient

An A3 poster: the headline reads from across a café, the details reward someone who walks up.

An A4 poster with the single word Listen set large over a soft gradient background

An A4 poster for close viewing can afford a single word and more empty space.

## Large posters and the 150 dpi rule

At 300 dpi, a 24 × 36 inch poster is 7200 × 10800 pixels, a heavy file for any design tool. Large posters are viewed from further away, and many print shops happily accept artwork at 150 dpi for them, which halves each dimension. Ask your printer what they want before you start, and design everything else at 300. [Image resolution for printing](https://gradiently.design/guide/image-resolution-for-print) shows how viewing distance changes the numbers.

| Poster | Pixels at 150 dpi | Typical viewing |
| --- | --- | --- |
| A2 | 2480 × 3508 | Across a room |
| 18 × 24 in | 2700 × 3600 | Across a room |
| A1 | 3508 × 4967 | From a corridor or street |
| 24 × 36 in | 3600 × 5400 | From a corridor or street |

A2 at 150 dpi is the same pixel size as A4 at 300 dpi, because A2 is exactly twice A4 in each direction.

> **Gradients scale better than photos** A photograph shot at a modest resolution will look soft on an A1 poster. A gradient or rendered background has no fixed pixels, so it can be drawn fresh at any size without losing sharpness.

## Setting up a poster file

1. **Pick the size with your printer** Confirm the trim size, the bleed they want and whether they print at 300 or 150 dpi.
2. **Create the page at the trim size** In Gradiently, A4, A3 and 18 × 24 are in the size list; A2 and anything else can be set as a custom size up to 8,000 pixels on each side, so a 24 × 36 inch poster is designed at 150 dpi (3600 × 5400).
3. **Keep words inside a safe margin** Leave at least 5 mm inside the trim on small posters and 10 mm on large ones.
4. **Export a print PDF** A PDF with bleed and crop marks tells the printer exactly where to cut. Read [print ready PDF](https://gradiently.design/guide/pdf-for-print) for the details.

If one poster becomes three sizes, design once and resize rather than starting again. Gradiently's Pro plan resizes a design to every size in one step and exports a print PDF with bleed and crop marks, and a Mark renders fresh at each size instead of being stretched. For layout ideas, see [poster design](https://gradiently.design/guide/poster-design) and [gradient posters](https://gradiently.design/guide/gradient-poster).

## FAQ

### What are the standard poster sizes?

A4, A3, A2 and A1 in most countries, and 11 × 17, 18 × 24 and 24 × 36 inches in the US and Canada.

### How many pixels is an A3 poster?

An A3 poster is 3508 × 4961 pixels at 300 dpi.

### What size is an 18 x 24 poster in pixels?

At 300 dpi an 18 × 24 inch poster is 5400 × 7200 pixels. At 150 dpi it is 2700 × 3600.

### Is A2 the same as 18 x 24?

No. A2 is 420 × 594 mm, roughly 16.5 × 23.4 inches, and a slightly narrower shape, so artwork for one needs adjusting for the other.

### What resolution should a poster be?

300 dpi at the printed size is the standard. For large posters seen from a distance, many printers accept 150 dpi.