The formula
centimetres = pixels ÷ ppi × 2.54
Where it comes from
A pixel has no physical size on its own: it depends on the resolution it is printed or displayed at. The resolution says how many pixels fit in an inch, and an inch is exactly 2.54 centimetres.
How to work it out by hand
- Divide the pixels by the resolution to get inches
- Multiply the inches by 2.54 for centimetres
- Going the other way, divide the centimetres by 2.54 and multiply by the resolution
What is worth knowing
The usual resolutions: 72 or 96 ppi for screens, 150 for acceptable home printing, 300 for quality printing and 600 or more for graphic arts. A photo 1,200 pixels wide looks perfect on screen but printed at 300 ppi it measures only 10 centimetres. That is why images pulled off the internet come out pixelated when printed large.
Pixels to centimetres, common values
The same image measures differently depending on the resolution it is used at: screens count 96 dots per inch and quality printing 300.
| Pixels | At 96 ppi (screen) | At 150 ppi | At 300 ppi (print) |
|---|---|---|---|
| 100 px | 2.65 cm | 1.69 cm | 0.85 cm |
| 120 px | 3.18 cm | 2.03 cm | 1.02 cm |
| 300 px | 7.94 cm | 5.08 cm | 2.54 cm |
| 448 px | 11.85 cm | 7.59 cm | 3.79 cm |
| 600 px | 15.88 cm | 10.16 cm | 5.08 cm |
| 1000 px | 26.46 cm | 16.93 cm | 8.47 cm |
| 1080 px | 28.57 cm | 18.29 cm | 9.14 cm |
| 1920 px | 50.80 cm | 32.51 cm | 16.26 cm |
| 2480 px | 65.62 cm | 41.99 cm | 21.00 cm |
| 4000 px | 105.83 cm | 67.73 cm | 33.87 cm |