100 DPI in pixels
At 100 DPI an inch is 100 pixels and a centimetre is 39.4 pixels. An A4 page is 827 × 1169 pixels and a US Letter page is 850 × 1100.
100 DPI is a round working figure for banners and large-format prints that are read from across a room.
At 100 DPI the pixels of a print blend together, for someone with 20/20 vision, from about 34.4 inches (87 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 100 DPI
| Size | Dimensions | Pixels at 100 DPI | Megapixels | Uncompressed |
|---|---|---|---|---|
| A0 | 841 × 1189 mm | 3311 × 4681 | 15 | 44 MB |
| A1 | 594 × 841 mm | 2339 × 3311 | 7.7 | 22 MB |
| A2 | 420 × 594 mm | 1654 × 2339 | 3.9 | 11 MB |
| A3 | 297 × 420 mm | 1169 × 1654 | 1.9 | 5.5 MB |
| A4 | 210 × 297 mm | 827 × 1169 | 0.97 | 2.8 MB |
| A5 | 148 × 210 mm | 583 × 827 | 0.48 | 1.4 MB |
| A6 | 105 × 148 mm | 413 × 583 | 0.24 | 705 KB |
| A7 | 74 × 105 mm | 291 × 413 | 0.12 | 352 KB |
| Letter | 8.5 × 11 in | 850 × 1100 | 0.94 | 2.7 MB |
| Legal | 8.5 × 14 in | 850 × 1400 | 1.2 | 3.4 MB |
| Tabloid | 11 × 17 in | 1100 × 1700 | 1.9 | 5.4 MB |
| Half Letter | 5.5 × 8.5 in | 550 × 850 | 0.47 | 1.3 MB |
| 4 × 6 in | 4 × 6 in | 400 × 600 | 0.24 | 703 KB |
| 5 × 7 in | 5 × 7 in | 500 × 700 | 0.35 | 1 MB |
| 8 × 10 in | 8 × 10 in | 800 × 1000 | 0.8 | 2.3 MB |
| 11 × 14 in | 11 × 14 in | 1100 × 1400 | 1.5 | 4.4 MB |
| 16 × 20 in | 16 × 20 in | 1600 × 2000 | 3.2 | 9.2 MB |
| 12 × 12 in | 12 × 12 in | 1200 × 1200 | 1.4 | 4.1 MB |
| 12 × 18 in | 12 × 18 in | 1200 × 1800 | 2.2 | 6.2 MB |
| 18 × 24 in | 18 × 24 in | 1800 × 2400 | 4.3 | 12 MB |
| 24 × 36 in | 24 × 36 in | 2400 × 3600 | 8.6 | 25 MB |
| Business card | 2 × 3.5 in | 200 × 350 | 0.07 | 205 KB |
Lengths at 100 DPI
| Inches | Pixels |
|---|---|
| 0.25 in | 25 |
| 0.5 in | 50 |
| 0.75 in | 75 |
| 1 in | 100 |
| 1.5 in | 150 |
| 2 in | 200 |
| 2.5 in | 250 |
| 3 in | 300 |
| 3.5 in | 350 |
| 4 in | 400 |
| 5 in | 500 |
| 6 in | 600 |
| Centimetres | Pixels |
|---|---|
| 0.5 cm | 20 |
| 1 cm | 39 |
| 1.5 cm | 59 |
| 2 cm | 79 |
| 2.5 cm | 98 |
| 3 cm | 118 |
| 3.5 cm | 138 |
| 4 cm | 157 |
| 4.5 cm | 177 |
| 5 cm | 197 |
| 6 cm | 236 |
| 7 cm | 276 |
| Millimetres | Pixels |
|---|---|
| 1 mm | 4 |
| 2 mm | 8 |
| 3 mm | 12 |
| 5 mm | 20 |
| 10 mm | 39 |
| 15 mm | 59 |
| 20 mm | 79 |
| 25 mm | 98 |
| 30 mm | 118 |
| 35 mm | 138 |
| 40 mm | 157 |
| 45 mm | 177 |
Changing an image to 100 DPI
The DPI stored in an image file is a label that says how large to print it. Changing the label to 100 without resampling keeps every pixel and only changes the print size: a 3000 × 2000 pixel photo becomes 30 × 20 inches. Resampling changes the number of pixels instead, and making an image larger that way does not add detail.