Poster Resolution Calculator
Check poster sizes from 18 x 24 inches to 36 x 48 inches against an image's pixel dimensions and a target DPI.
| Size | Needed pixels | Your effective DPI | Suitable? |
|---|---|---|---|
| 18 x 24 in | 5400 x 7200 | 167 DPI | No — image too small |
| 24 x 36 in | 7200 x 10800 | 125 DPI | No — image too small |
| 27 x 40 in | 8100 x 12000 | 111 DPI | No — image too small |
| 36 x 48 in | 10800 x 14400 | 83 DPI | No — image too small |
Suitability here is only about pixel count versus the chosen DPI. Viewing distance, printer capability and image content also affect the final print.
How to use this calculator
1. Enter image dimensions. 2. Pick a target DPI. 3. Read, for each preset size, the pixels required and whether your image meets them.
Formula
Effective DPI = Pixel width / Print width in inches. Compare it with your target DPI for each preset size.
Paper sizes and viewing distance
| Size | Millimeters | Pixels at 300 DPI |
|---|---|---|
| A5 | 148 x 210 mm | 1748 x 2480 px |
| A4 | 210 x 297 mm | 2480 x 3508 px |
| A3 | 297 x 420 mm | 3508 x 4961 px |
| Viewing situation | Target DPI | Why |
|---|---|---|
| Close-up photo | 300 | Held in the hand; fine detail is visible. |
| Wall poster | 150 | Viewed from a few feet away; finer detail cannot be resolved. |
| Billboard | 72 | Viewed from far away; 300 DPI would be wasted pixels. |
Frequently asked questions
Can a poster use lower DPI than a photo print?
Yes. Posters are usually viewed from further away, so 150 DPI is often acceptable, while a photo held in the hand benefits from 300 DPI.