How to convert pixels to inches
Divide the pixels by the resolution: inches = pixels ÷ PPI. Pixels have no size of their own. A length in inches exists only once you say how many pixels go into each inch, and that number is the resolution, in pixels per inch (PPI). At 96 PPI, 1920 pixels make 20 inches; at 300 PPI the same pixels make 6.4 inches. For centimetres, multiply the inches by 2.54. The other way round, pixels = inches × PPI.
Which resolution to use
| Resolution | Used for | One inch is |
|---|---|---|
| 72 ppi | Many image files, older Mac screens | 72 px |
| 96 ppi | Screens: CSS and Windows | 96 px |
| 150 ppi | Large prints seen from a distance | 150 px |
| 300 ppi | Photo prints and magazines | 300 px |
| 600 ppi | Line art, text and scans | 600 px |
Pixels to inches at 96 and 300 PPI
| Pixels | At 96 PPI | At 300 PPI |
|---|---|---|
| 100 px | 1.04 in (2.65 cm) | 0.33 in (0.85 cm) |
| 500 px | 5.21 in (13.23 cm) | 1.67 in (4.23 cm) |
| 1080 px | 11.25 in (28.57 cm) | 3.6 in (9.14 cm) |
| 1200 px | 12.5 in (31.75 cm) | 4 in (10.16 cm) |
| 1920 px | 20 in (50.8 cm) | 6.4 in (16.26 cm) |
| 3000 px | 31.25 in (79.38 cm) | 10 in (25.4 cm) |
| 4032 px | 42 in (106.68 cm) | 13.44 in (34.14 cm) |
Why 96 pixels make an inch on screen
In CSS, the language of web pages, an inch is defined as 96 pixels, and Windows uses the same 96 as its standard. A real screen packs its own number of physical pixels into an inch, so an inch on screen is seldom an inch on a ruler: it is a fixed unit for design. When a web or app design gives a size in inches or centimetres, 96 PPI is the number it means.
Is DPI the same as PPI?
Strictly, DPI (dots per inch) says how many dots of ink a printer lays down, and PPI says how many pixels of an image go into an inch. People often say DPI for both. For this conversion they are used the same way: when a print shop asks for 300 DPI, set 300 and read the size. The DPI value written in an image file changes nothing in its pixels.
Converting a print size to pixels
For a print, work the other way: type the size in inches or centimetres, set 300 PPI and read the pixels you need. An A4 page, 21 × 29.7 cm, needs 2480 × 3508 pixels at 300 PPI. A US Letter page, 8.5 × 11 inches, needs 2550 × 3300 pixels.