72 DPI in pixels
At 72 DPI an inch is 72 pixels and a centimetre is 28.3 pixels. An A4 page is 595 × 842 pixels and a US Letter page is 612 × 792.
72 DPI is the old screen convention: early Macintosh displays showed 72 pixels to the inch, matching the 72 points in an inch of type. Many image files still carry a 72 DPI tag for that reason.
At 72 DPI the pixels of a print blend together, for someone with 20/20 vision, from about 47.7 inches (121 cm) away. Closer than that, an eye can pick out the pixel grid; further back, more resolution adds nothing you can see.
Paper and photo sizes at 72 DPI
| Size | Dimensions | Pixels at 72 DPI | Megapixels | Uncompressed |
|---|---|---|---|---|
| A0 | 841 × 1189 mm | 2384 × 3370 | 8 | 23 MB |
| A1 | 594 × 841 mm | 1684 × 2384 | 4 | 11 MB |
| A2 | 420 × 594 mm | 1191 × 1684 | 2 | 5.7 MB |
| A3 | 297 × 420 mm | 842 × 1191 | 1 | 2.9 MB |
| A4 | 210 × 297 mm | 595 × 842 | 0.5 | 1.4 MB |
| A5 | 148 × 210 mm | 420 × 595 | 0.25 | 732 KB |
| A6 | 105 × 148 mm | 298 × 420 | 0.13 | 367 KB |
| A7 | 74 × 105 mm | 210 × 298 | 0.06 | 183 KB |
| Letter | 8.5 × 11 in | 612 × 792 | 0.48 | 1.4 MB |
| Legal | 8.5 × 14 in | 612 × 1008 | 0.62 | 1.8 MB |
| Tabloid | 11 × 17 in | 792 × 1224 | 0.97 | 2.8 MB |
| Half Letter | 5.5 × 8.5 in | 396 × 612 | 0.24 | 710 KB |
| 4 × 6 in | 4 × 6 in | 288 × 432 | 0.12 | 365 KB |
| 5 × 7 in | 5 × 7 in | 360 × 504 | 0.18 | 532 KB |
| 8 × 10 in | 8 × 10 in | 576 × 720 | 0.41 | 1.2 MB |
| 11 × 14 in | 11 × 14 in | 792 × 1008 | 0.8 | 2.3 MB |
| 16 × 20 in | 16 × 20 in | 1152 × 1440 | 1.7 | 4.7 MB |
| 12 × 12 in | 12 × 12 in | 864 × 864 | 0.75 | 2.1 MB |
| 12 × 18 in | 12 × 18 in | 864 × 1296 | 1.1 | 3.2 MB |
| 18 × 24 in | 18 × 24 in | 1296 × 1728 | 2.2 | 6.4 MB |
| 24 × 36 in | 24 × 36 in | 1728 × 2592 | 4.5 | 13 MB |
| Business card | 2 × 3.5 in | 144 × 252 | 0.04 | 106 KB |
Lengths at 72 DPI
| Inches | Pixels |
|---|---|
| 0.25 in | 18 |
| 0.5 in | 36 |
| 0.75 in | 54 |
| 1 in | 72 |
| 1.5 in | 108 |
| 2 in | 144 |
| 2.5 in | 180 |
| 3 in | 216 |
| 3.5 in | 252 |
| 4 in | 288 |
| 5 in | 360 |
| 6 in | 432 |
| Centimetres | Pixels |
|---|---|
| 0.5 cm | 14 |
| 1 cm | 28 |
| 1.5 cm | 43 |
| 2 cm | 57 |
| 2.5 cm | 71 |
| 3 cm | 85 |
| 3.5 cm | 99 |
| 4 cm | 113 |
| 4.5 cm | 128 |
| 5 cm | 142 |
| 6 cm | 170 |
| 7 cm | 198 |
| Millimetres | Pixels |
|---|---|
| 1 mm | 3 |
| 2 mm | 6 |
| 3 mm | 9 |
| 5 mm | 14 |
| 10 mm | 28 |
| 15 mm | 43 |
| 20 mm | 57 |
| 25 mm | 71 |
| 30 mm | 85 |
| 35 mm | 99 |
| 40 mm | 113 |
| 45 mm | 128 |
Changing an image to 72 DPI
The DPI stored in an image file is a label that says how large to print it. Changing the label to 72 without resampling keeps every pixel and only changes the print size: a 3000 × 2000 pixel photo becomes 41.67 × 27.78 inches. Resampling changes the number of pixels instead, and making an image larger that way does not add detail.