Pixel to CM Converter
A pixel has no physical size until you say how many fit in an inch. Enter a value, pick the DPI your printer, form or design tool uses, and read the answer in centimeters, inches, millimeters or points. The same tool converts file sizes from MB to KB.
Unit Converter
Nothing is uploaded; the code is generated for you to download.
Pixels per inch used to turn pixels into cm, mm or inches. 96 is the screen/CSS standard; use 300 for photos and print, or the DPI a form specifies. At 300 DPI, 1 cm = 118 px.
Windows and most upload forms count 1 KB = 1024 bytes (1 MB = 1024 KB). macOS and disk makers use 1000. The difference is about 5% at MB size.
How many digits to show after the decimal point in the result.
Also shows the matching other side at this ratio, e.g. 1920 px wide at 16:9 is 1080 px tall.
First number of the ratio, e.g. 5 for 5:7.
Second number of the ratio, e.g. 7 for 5:7.
How to use this tool
- 1
Type the number
Enter the value in Value, for example 600 for a 600 px image or 3.5 for 3.5 cm. No file is uploaded; the math runs on the page.
- 2
Set the units and DPI
Choose From and To. For lengths, set Pixel density under Advanced settings: 96 for screens and CSS, 300 for print. For file sizes, pick whether 1 KB is 1024 or 1000 bytes.
- 3
Read and copy the result
The answer updates as you type, rounded to the number of Decimal places you chose. Turn on Keep aspect ratio to see the matching height for 16:9, 4:5 or a custom ratio.
CM to pixel table at 72, 150 and 300 DPI
| cm | Pixels at | ||
|---|---|---|---|
| 72 DPI | 150 DPI | 300 DPI | |
| 1 | 28 | 59 | 118 |
| 2.5 | 71 | 148 | 295 |
| 3.5 | 99 | 207 | 413 |
| 5 | 142 | 295 | 591 |
| 10 | 283 | 591 | 1181 |
| 21 (A4 width) | 595 | 1240 | 2480 |
| 29.7 (A4 height) | 842 | 1754 | 3508 |
The 72 DPI column is the old Mac screen convention and is still the default in many export dialogs. The 150 column is enough for drafts and office printouts, and 300 is the standard for photos, exam portals and print shops. For screens and web layouts use 96: the CSS specification fixes 1 in at 96 px, so 1 cm in a stylesheet is always 37.8 px, whatever the monitor.
Rounding matters at small sizes. A 3.5 cm photo at 300 DPI is 413.4 px, and most forms accept 413. If a form gives both a pixel size and a cm size, the pixel size is the one the upload checker measures; the cm figure is only what it would print at.
Millimeters work the same way with a factor of 25.4 instead of 2.54. Points, the unit used for type and PDF page sizes, are fixed at 72 per inch, so a 12 pt line is exactly 1/6 in tall.
What DPI means for pixel to cm conversion
- DPI (dots per inch)PPI · pixel density · resolution
- How many image pixels are placed along one inch when the image is printed or measured. Strictly, pixels per inch (PPI) is the image term and DPI is the printer term, but forms, apps and this converter use DPI for both.
MB to KB and other file size conversions
- in 1 MB on Windows and most forms
- 1024 KB
- in 1 MB on macOS and drive labels
- 1000 KB
- in 5 MB, binary rule
- 5120 KB
- gap between the two at MB scale
- ≈ 5%
Set From to MB and To to KB to convert file sizes, and choose the rule in 1 KB equals. The International Electrotechnical Commission introduced the names KiB and MiB in 1998 to separate the binary units from the decimal ones, but most software still prints KB and MB for both. Windows File Explorer divides by 1024; macOS switched to dividing by 1000 with Mac OS X 10.6 Snow Leopard in 2009.
This matters when a portal says an image must be under 100 KB. If the file shows as 101 KB on a Mac, it may already pass on a 1024-based checker, but there is no way to know in advance. Bring it comfortably under with Compress image to 100 KB rather than relying on the difference.
Pixel, cm and KB questions
How many pixels are in 1 cm?
It depends on the DPI. At 96 DPI, the screen and CSS standard, 1 cm is 37.8 px. At 300 DPI, the usual print resolution, 1 cm is 118.1 px, and at 72 DPI it is 28.3 px.
What is the formula for converting px to cm?
Divide the pixels by the DPI to get inches, then multiply by 2.54. For 1200 px at 300 DPI that is 1200 ÷ 300 × 2.54 = 10.16 cm. Going the other way, cm ÷ 2.54 × DPI gives pixels.
Which DPI should I use for a form that asks for a photo in cm?
Use 300 DPI unless the form names another value. A 3.5 × 4.5 cm passport photo at 300 DPI is 413 × 531 px, which is what most photo portals expect. Our guide to passport photo sizes in cm, inches and pixels lists more countries.
Is 1 MB 1000 KB or 1024 KB?
Both conventions are in use. Windows and most upload forms count 1 MB as 1024 KB, while macOS and drive makers use 1000. When a form says the file must be under 2 MB, assume 2048 KB is the limit only if it was built on Windows conventions; staying under 2000 KB is safe either way.
Why does my image print smaller than it looks on screen?
Screens show one image pixel per screen pixel, while a printer packs 300 of them into each inch. A 1200 px wide photo fills a laptop screen but prints only 10.16 cm wide at 300 DPI. To print larger, you need more pixels or a lower DPI.
Does changing the DPI make the image file larger?
No. DPI is a single number stored in the file's metadata; the pixel count and the file size stay the same. Only resizing the pixels changes the size, which is what Resize image to cm does.
- Resize Image in cmResize an image to an exact size in centimeters: type width and height in cm, choose the DPI, and get the right pixel count for print or a form.
- Resize Image in mmType width and height in millimeters, pick the DPI, and get the exact pixels: 35 × 45 mm at 300 DPI becomes 413 × 531 px. For photos, ID cards and print.
- 2x2 Picture Size in PixelsA 2x2 picture is 600 × 600 px at 300 DPI. Online forms take 600 to 1200 px squares; the head is 300–413 px tall. Make the exact file from any photo.
- Image Resizer in Pixels and KBSet width and height in pixels and a maximum in KB in one step: 200 × 230 px under 50 KB is preset, the format most exam and job forms ask for.
- Compress Image to 100 KBReduce image size to 100 KB for job portals, visa forms and email. Hits the target exactly, keeps the picture sharp, strips location data. Free.