Pixels to CM Converter (DPI)
Pixels ↔ cm, mm and inches at 72, 96, 300 or any DPI — for prints, forms and screens.
Type a number, or a number with its unit: 1000 px, 10 cm, 4 in, 12 pt.
Forms that ask for a photo of a set size usually also set the pixel size, file size and format — check the official specification.
84.67 mm · 3.333 in · 240 pt
| Unit | Value |
|---|---|
| Pixels | 1000 |
| Centimetres | 8.467 |
| Millimetres | 84.67 |
| Inches | 3.333 |
| Points (1/72 in) | 240 |
About the Pixels to CM Converter (DPI)
Pixels have no physical size until you choose how many of them go into an inch. Pick a resolution — 96 DPI for web pages, 300 DPI for photo prints, or any other — and convert pixels to centimetres, millimetres, inches and points, or back.
Three more calculators cover the common print jobs: the print size of an image (6000 × 4000 px is 50.8 × 33.9 cm at 300 DPI), the DPI an image gets when printed at a size you choose, and the pixels needed for a physical size, such as 413 × 531 px for a 3.5 × 4.5 cm photo at 300 DPI. You can also pick an image to fill in its pixel size and see the DPI stored in the file — only the size is read, and nothing is uploaded.
How to use it
- Choose the resolution: 72, 96 (the CSS pixel of web pages), 150, 200, 300 (print), 600 or a custom DPI.
- In Convert, type a value and pick its unit (or type it with the unit, such as
10 cmor1000 px); every unit appears in the table. - In Print size, type the image’s width and height in pixels — or pick the image — to see how large it prints at each resolution.
- In DPI at a size, add the print size to see the resolution across and down, and whether the shapes match.
- In Pixels for a size, pick a common size or type one to get the pixel dimensions, rounded to the nearest pixel and rounded up.
Examples
1000 px, 300 DPI
8.467 cm (84.67 mm, 3.333 in)
1000 ÷ 300 = 3.333 in; × 2.54 = 8.467 cm.
3.5 × 4.5 cm, 300 DPI
413 × 531 px
3.5 ÷ 2.54 × 300 = 413.39 and 4.5 ÷ 2.54 × 300 = 531.496: the nearest whole pixels are 413 × 531, and 414 × 532 if the resolution must not drop below 300 DPI.
210 × 297 mm
2480 × 3508 px at 300 DPI · 1240 × 1754 px at 150 DPI
6000 × 4000 px, 300 DPI
50.8 × 33.87 cm (20 × 13.33 in)
1800 × 1200 px on 6 × 4 in
300 DPI across and down
1 cm, 96 DPI
37.8 px
CSS fixes 1 in = 96 px, so 1 cm = 96 ÷ 2.54 px.
Common uses
- Preparing a photo or signature for an online form that asks for a size in cm and a resolution.
- Checking whether a picture is sharp enough to print as a poster, a photo book page or a 6 × 4 in print.
- Setting a canvas size in pixels for A4 or Letter artwork at 300 DPI.
- Converting CSS pixels to physical units for print stylesheets (1 in = 96 px).
The formula
One inch is exactly 2.54 cm (NIST Handbook 44, Appendix C), and DPI (or PPI) is the number of pixels in one inch, so:
- cm = pixels ÷ DPI × 2.54 — 1000 px at 300 DPI = 8.467 cm
- pixels = cm ÷ 2.54 × DPI — 10 cm at 300 DPI = 1181 px
- DPI = pixels ÷ inches — 1800 px over 6 in = 300 DPI
- points = inches × 72
On the web, CSS defines 1 in = 96 px = 72 pt (CSS Values and Units), which is why 96 DPI is the screen preset.
DPI, PPI and the number in your file
PPI (pixels per inch) describes an image or a screen; DPI (dots per inch) strictly describes a printer’s ink dots, but the two are used for the same idea when sizing images. The DPI stored in a JPEG or PNG is only a note about the intended print size: changing it does not add or remove pixels, so a 72-DPI and a 300-DPI copy of the same picture are identical on screen. What decides print sharpness is the pixel count divided by the print size.
How much resolution a print needs
A common rule of thumb is 300 DPI for prints looked at closely (photos, ID photos, brochures) and 150 DPI or less for posters and banners seen from a distance. The DPI at a size calculator shows the resolution your image would really get, and warns when the image and the paper have different shapes, so the print would be cropped or stretched.
Limitations
- Screens differ: a CSS pixel is 1/96 in by definition, but a phone or a high-density laptop shows it with several device pixels, so on-screen sizes are real only by chance (use the Online Ruler to calibrate).
- Form and passport photo rules also set head size, background, file size and format; this tool only does the size arithmetic — always check the official specification.
- Reading an image’s pixel size works for JPEG, PNG, GIF, WebP and BMP headers, and for other formats your browser can open.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How many pixels is 1 cm?
It depends on the resolution: 37.8 px at 96 DPI (web pages) and 118.1 px at 300 DPI (print). Pixels = cm ÷ 2.54 × DPI.
What is 3.5 × 4.5 cm in pixels?
At 300 DPI it is 413 × 531 px (413.39 × 531.496 before rounding). At 600 DPI it is 827 × 1063 px. Check the form’s own pixel and file-size limits too.
What is A4 in pixels?
A4 (210 × 297 mm) is 2480 × 3508 px at 300 DPI, 1240 × 1754 px at 150 DPI and 794 × 1123 px at 96 DPI.
Does changing an image to 300 DPI make it sharper?
No. The DPI number in the file only changes the size it prints at. To print sharper at the same size you need more pixels, or a smaller print.
What is the difference between DPI and PPI?
PPI counts pixels per inch in an image or on a screen; DPI counts a printer’s dots per inch. For sizing images people use them interchangeably.