240 DPI in pixels
At 240 DPI an inch is 240 pixels and a centimetre is 94.5 pixels. An A4 page is 1984 × 2806 pixels and a US Letter page is 2040 × 2640.
240 DPI is the default print resolution in Adobe Lightroom, and close enough to 300 that few people can tell the two apart in a photo print.
At 240 DPI the pixels of a print blend together, for someone with 20/20 vision, from about 14.3 inches (36 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 240 DPI
| Size | Dimensions | Pixels at 240 DPI | Megapixels | Uncompressed |
|---|---|---|---|---|
| A0 | 841 × 1189 mm | 7946 × 11235 | 89 | 255 MB |
| A1 | 594 × 841 mm | 5613 × 7946 | 45 | 128 MB |
| A2 | 420 × 594 mm | 3969 × 5613 | 22 | 64 MB |
| A3 | 297 × 420 mm | 2806 × 3969 | 11 | 32 MB |
| A4 | 210 × 297 mm | 1984 × 2806 | 5.6 | 16 MB |
| A5 | 148 × 210 mm | 1398 × 1984 | 2.8 | 7.9 MB |
| A6 | 105 × 148 mm | 992 × 1398 | 1.4 | 4 MB |
| A7 | 74 × 105 mm | 699 × 992 | 0.69 | 2 MB |
| Letter | 8.5 × 11 in | 2040 × 2640 | 5.4 | 15 MB |
| Legal | 8.5 × 14 in | 2040 × 3360 | 6.9 | 20 MB |
| Tabloid | 11 × 17 in | 2640 × 4080 | 11 | 31 MB |
| Half Letter | 5.5 × 8.5 in | 1320 × 2040 | 2.7 | 7.7 MB |
| 4 × 6 in | 4 × 6 in | 960 × 1440 | 1.4 | 4 MB |
| 5 × 7 in | 5 × 7 in | 1200 × 1680 | 2 | 5.8 MB |
| 8 × 10 in | 8 × 10 in | 1920 × 2400 | 4.6 | 13 MB |
| 11 × 14 in | 11 × 14 in | 2640 × 3360 | 8.9 | 25 MB |
| 16 × 20 in | 16 × 20 in | 3840 × 4800 | 18 | 53 MB |
| 12 × 12 in | 12 × 12 in | 2880 × 2880 | 8.3 | 24 MB |
| 12 × 18 in | 12 × 18 in | 2880 × 4320 | 12 | 36 MB |
| 18 × 24 in | 18 × 24 in | 4320 × 5760 | 25 | 71 MB |
| 24 × 36 in | 24 × 36 in | 5760 × 8640 | 50 | 142 MB |
| Business card | 2 × 3.5 in | 480 × 840 | 0.4 | 1.2 MB |
Lengths at 240 DPI
| Inches | Pixels |
|---|---|
| 0.25 in | 60 |
| 0.5 in | 120 |
| 0.75 in | 180 |
| 1 in | 240 |
| 1.5 in | 360 |
| 2 in | 480 |
| 2.5 in | 600 |
| 3 in | 720 |
| 3.5 in | 840 |
| 4 in | 960 |
| 5 in | 1,200 |
| 6 in | 1,440 |
| Centimetres | Pixels |
|---|---|
| 0.5 cm | 47 |
| 1 cm | 94 |
| 1.5 cm | 142 |
| 2 cm | 189 |
| 2.5 cm | 236 |
| 3 cm | 283 |
| 3.5 cm | 331 |
| 4 cm | 378 |
| 4.5 cm | 425 |
| 5 cm | 472 |
| 6 cm | 567 |
| 7 cm | 661 |
| Millimetres | Pixels |
|---|---|
| 1 mm | 9 |
| 2 mm | 19 |
| 3 mm | 28 |
| 5 mm | 47 |
| 10 mm | 94 |
| 15 mm | 142 |
| 20 mm | 189 |
| 25 mm | 236 |
| 30 mm | 283 |
| 35 mm | 331 |
| 40 mm | 378 |
| 45 mm | 425 |
Changing an image to 240 DPI
The DPI stored in an image file is a label that says how large to print it. Changing the label to 240 without resampling keeps every pixel and only changes the print size: a 3000 × 2000 pixel photo becomes 12.5 × 8.33 inches. Resampling changes the number of pixels instead, and making an image larger that way does not add detail.