Printing guide
What DPI for printing?
DPI (dots per inch) controls how sharp a printed image looks. The short answer: 300 DPI for anything held in the hand, 150 DPI for posters viewed from a distance, 72 DPI never (unless the output is only ever going to a screen).
| Resolution | Pixels for a 10 × 15 cm print | Relative detail | Verdict |
|---|---|---|---|
| 72 DPI | 283 × 425 | 1× | Screen only. Visible pixels on paper. |
| 150 DPI | 591 × 886 | 4.3× | Fine for posters and anything seen from a step back. |
| 300 DPI | 1181 × 1772 | 17× | The commercial standard for held-in-hand printing. |
The middle column is the part that settles the argument: resolution counts in two directions, so going from 72 to 150 DPI does not merely double the detail, it multiplies it more than fourfold. That is also why the step from 150 to 300 costs so much more file size than it appears to — and why it is worth spending only where the print will be held close enough to see it.
The standard values
| DPI | When to use | A4 page in pixels |
|---|---|---|
| 72 | Screen only — older displays, web mockups | 595 × 842 |
| 96 | Default for Windows screens and web output | 794 × 1123 |
| 150 | Large posters, billboards, proofing prints | 1240 × 1754 |
| 200 | Internal/draft commercial print | 1654 × 2339 |
| 300 | Standard for commercial print — cards, flyers, books | 2480 × 3508 |
| 600 | Fine detail — letterpress, engraving, archival prints | 4961 × 7016 |
Why 300?
At a 30 cm reading distance, the human eye resolves roughly 300 line pairs per inch. Pushing beyond that produces output that looks the same to the eye but takes more time and disk space to process. Commercial print machines are designed around this number, and almost every print spec sheet refers to 300 DPI as the minimum quality threshold.
The 150 DPI exception
Viewing distance matters. Anything that will be seen from further away can use lower DPI without visible quality loss. A 24 × 36 inch poster viewed from 2 m away looks just as sharp at 150 DPI as at 300. The math is simple: doubling viewing distance roughly halves the DPI you need.
For really large outdoor signage (billboards, building wraps, vehicle graphics) the standard can drop to 72 DPI or lower — at 10 m+ the eye genuinely cannot tell the difference.
A common mistake
Changing an image's DPI metadata without resampling the pixels does nothing useful. Taking a 600 × 600 pixel image and setting its DPI to 300 just means it now claims to be 2 × 2 inches. If you print it at 6 × 6 inches it will still look pixellated — because the actual pixel count is too low for the physical size. What matters is pixel count, not the metadata.
Frequently asked questions
What does DPI mean?
DPI stands for "dots per inch". It is the density of ink dots a printer lays down across one linear inch of paper. Higher DPI means finer detail. The same concept applied to digital images is sometimes called PPI (pixels per inch); the two are used interchangeably in casual conversation.
Why is 300 DPI the standard for print?
At normal reading distance (roughly 30 cm), the human eye can just barely resolve detail at 300 DPI. Pushing higher gives diminishing returns. Most commercial printers are calibrated around this number, and it produces visibly sharp output for text, logos and photos.
Is 150 DPI better than 72 DPI?
For anything printed, yes — decisively, and it is not a close call. At the same physical size a 150 DPI image carries just over four times the pixels of a 72 DPI one, because resolution counts in two dimensions: doubling it roughly quadruples the pixel count. A photo printed at 72 DPI shows visible pixel structure at arm’s length; the same photo at 150 DPI looks clean from half a metre and acceptable close up. On screen the comparison is meaningless, because a screen ignores the DPI figure entirely and simply shows the pixels it is given.
When is 150 DPI enough?
For posters and signage viewed from more than 1.5–2 metres away. The eye cannot resolve 300 DPI detail at that distance, so a 150 DPI image looks identical. The benefit is half the file size and half the upload time.
Why is 72 DPI only for screens?
Historically, 72 DPI was the standard screen resolution (the value comes from early Apple display calibration). Modern screens are much denser, but 72 DPI is still the default save value for many image-export tools. Files saved at 72 DPI carry too few pixels per inch to print sharply at any meaningful size.
How do I check the DPI of an image?
Right-click → Properties on Windows, or Cmd-I (Get Info) on macOS, then look for "DPI" or "Resolution" in the metadata. Better still: open the file in any image editor and look at the document setup. Note that DPI is metadata only — what matters is the actual pixel count divided by the printed size in inches.
Working from a specific photograph rather than a target size? The image print quality analyser reads its pixel dimensions and embedded DPI in your browser and reports the largest size it still prints well at. It also answers the question people usually ask instead — whether a file of so many kilobytes is enough — by showing what file size does and does not tell you.