DPI and print size reference
How many pixels does a 30 × 40 cm print need? 3,543 × 4,724 at 300 DPI. This page gives the numbers for common sizes and explains when 300 DPI is overkill.
The conversion, in one sentence
Pixels = print size in centimetres ÷ 2.54 × DPI. That is the whole formula. Everything else is deciding which DPI you actually need, because that single choice can multiply a file size by sixteen without any visible difference on screen.
Print sizes and the pixels they need
A print at 300 DPI looks sharp from close up - the standard for anything a client will hold. 150 DPI is the practical minimum for posters and large formats viewed from more than arm's length. 72 DPI is a legacy web figure: it is not a real requirement, it is simply what browsers historically assumed.
| Print size | In inches | Pixels at 300 DPI | Pixels at 150 DPI | Pixels at 72 DPI |
|---|---|---|---|---|
| 10 × 15 cm | 4 × 6 in | 1181 × 1772 | 591 × 886 | 283 × 425 |
| 13 × 18 cm | 5 × 7 in | 1535 × 2126 | 768 × 1063 | 369 × 510 |
| A4 (21 × 29.7 cm) | 8.3 × 11.7 in | 2480 × 3508 | 1240 × 1754 | 595 × 842 |
| A3 (29.7 × 42 cm) | 11.7 × 16.5 in | 3508 × 4961 | 1754 × 2480 | 842 × 1191 |
| 20 × 25 cm | 8 × 10 in | 2362 × 2953 | 1181 × 1476 | 567 × 709 |
| 20 × 30 cm | 8 × 12 in | 2362 × 3543 | 1181 × 1772 | 567 × 850 |
| 30 × 40 cm | 12 × 16 in | 3543 × 4724 | 1772 × 2362 | 850 × 1134 |
| 30 × 45 cm | 12 × 18 in | 3543 × 5315 | 1772 × 2657 | 850 × 1276 |
| 40 × 50 cm | 16 × 20 in | 4724 × 5906 | 2362 × 2953 | 1134 × 1417 |
| 40 × 60 cm | 16 × 24 in | 4724 × 7087 | 2362 × 3543 | 1134 × 1701 |
What each resolution is actually for
- 300 DPI: photo prints, brochures, anything held in the hand or inspected up close
- 150 DPI: posters and large prints seen from a distance, where 300 DPI would produce a file nobody needs
- 96 DPI: the practical baseline for web images, though what actually matters on screen is pixel dimensions, not DPI at all
- 72 DPI: legacy value from early Macintosh displays; keep it only if a specific tool insists
The DPI field on a web image does nothing
A JPEG can carry a DPI value in its metadata, and it changes nothing about what the browser displays - a 3000-pixel-wide file is 3000 pixels wide whether the tag says 72 or 300. DPI only becomes real when the image is printed, and then it is the printer dialog that interprets it. If a form asks you for "300 DPI", it almost always means "enough pixels for the stated physical size", which you can check with the table above.
The converse matters just as much: raising the DPI tag does not add detail. Resampling a 1000-pixel image up to 300 DPI at A4 produces a bigger file with exactly the same information, just softer.
All pixel figures are rounded to the nearest pixel. Print sizes are nominal; a print shop may trim a few millimetres.
Cite this page
Free to cite. Copy the reference below, or link to this page directly.
PicConv. "DPI and print size reference". https://picconv.com/resources/dpi-print-sizes/ (accessed 2026-11-01).
Tools that use this
Resize Image
Resize one or many images by exact pixels or by percentage while keeping the aspect ratio. High-quality downscaling, optional WebP or PNG output and batch ZIP download.
→Compress Image to Target Size
Shrink a JPG, PNG or WebP file to an exact size such as 100 KB, 200 KB or 1 MB. The quality is lowered step by step and, if necessary, the dimensions are reduced until the file fits the limit you need.
→Compress Image
Shrink JPG, PNG and WebP images with quality, output-format and maximum-width controls. Batch several files at once, compare before/after sizes and download everything as a ZIP.
→ID Photo Maker
Crop a portrait to an official photo size (1 inch, 2 inch, passport, visa or your own dimensions), optionally place it on a coloured background and generate a printable 6-inch sheet with eight copies.
→Frequently asked questions
How many pixels is 300 DPI at A4?
A4 is 21 × 29.7 cm, which at 300 DPI is 2,480 × 3,508 pixels - about 8.7 megapixels. At 150 DPI it is 1,240 × 1,754.
Is 150 DPI enough for printing?
For a poster or a large format seen from a metre away, yes. For a photo you will hold in your hand, 300 DPI is the safer standard. The viewing distance matters more than the number itself.
Does changing the DPI tag change the file?
Only the metadata, plus the file size of the tag itself. The pixels are untouched, so neither sharpness nor print quality changes. To actually change resolution you must resample the image, which either interpolates new pixels (bigger, softer) or discards some (smaller, sharper).
Why do my phone photos look fine at 96 DPI?
Because the screen only cares about pixel dimensions. A 4000-pixel-wide photo shown at 800 pixels wide is downscaled for display; the DPI value in its metadata is never consulted.
How do I resize an image to a target pixel size?
Use a resizer that takes width or height in pixels, and keep the aspect ratio locked. Resizing down removes pixels and always looks clean; resizing up interpolates and softens, so start from the largest source you have.