72 DPI vs 300 DPI
For print, use 300. For a screen it makes no difference: a screen shows pixels and ignores the DPI number in the file. The same 1200 × 1800 pixel image prints at 16.7 × 25 inches at 72 DPI and at 4 × 6 inches at 300 DPI, and looks identical on a monitor either way.
| 72 DPI | 300 DPI | |
|---|---|---|
| Pixels in an inch | 72 | 300 |
| Pixels in a centimetre | 28.3 | 118.1 |
| Pixels in a square inch | 5,184 | 90,000 |
| 4 × 6 in photo | 288 × 432 | 1200 × 1800 |
| A4 page | 595 × 842 | 2480 × 3508 |
| US Letter page | 612 × 792 | 2550 × 3300 |
| A4 in megapixels | 0.5 | 8.7 |
| A4 uncompressed | 1.4 MB | 25 MB |
| Pixels blend from | 47.7 inches (121 cm) | 11.5 inches (29 cm) |
300 DPI has 17.4 times the pixels of 72 DPI at the same print size. “Pixels blend from” is the distance at which 20/20 vision stops separating them.
When 72 DPI is the right choice
- Never as a quality setting. 72 DPI is only a tag left over from early Macintosh screens.
- A print meant to be seen from more than about 1.2 metres (4 feet) away can get by at 72 DPI, such as a banner across a hall.
When 300 DPI is the right choice
- Anything printed and held in the hand: photos, flyers, cards, books.
- Files sent to a print shop, which will usually ask for 300 DPI at the final size.
Why
The common advice to “save for web at 72 DPI” changes nothing a browser can see. What matters on a screen is the pixel size of the image. Changing an image from 72 to 300 DPI without resampling keeps every pixel and only changes how large it prints. Resampling up to reach 300 DPI at a bigger size invents pixels and does not add detail.