Resize Image in CM — Free Online Tool
Resize your images to precise centimeter dimensions for passport photos, official documents, ID cards, and professional prints. Automatic DPI-to-pixel conversion built in.
Why Resize Images in Centimeters?
Physical documents and printed photos are measured in centimeters, not pixels. When you need to submit a 3.5 × 4.5 cm passport photo, print an ID card image at 2.5 × 3.5 cm, or prepare a photo for a 4 × 6 cm visa application, you need your digital image sized to those exact physical dimensions at the correct DPI.
Our tool lets you enter dimensions in CM directly — no manual conversion needed. It automatically calculates the pixel dimensions based on your DPI setting (300 DPI for print, 72 DPI for screen).
Switch to "cm" unit in the dimension fields • Set DPI for print accuracy
Common CM Sizes for Photos & Documents
Reference table with pixel equivalents at 300 DPI (standard print resolution):
| Size (CM) | Common Use | Pixels at 300 DPI |
|---|---|---|
| 3.5 × 4.5 cm | Passport photo (India, EU, UK) | 413 × 531 px at 300 DPI |
| 2.5 × 3.5 cm | ID card, driving license | 295 × 413 px at 300 DPI |
| 5.1 × 5.1 cm | US passport (2×2 inches) | 600 × 600 px at 300 DPI |
| 4 × 4 cm | Visa applications, OCI card | 472 × 472 px at 300 DPI |
| 4 × 6 cm | Work permit, some EU visas | 472 × 709 px at 300 DPI |
| 3 × 4 cm | Japanese visa, JLPT forms | 354 × 472 px at 300 DPI |
| 5 × 7 cm | Stamp size for applications | 591 × 827 px at 300 DPI |
| 10 × 15 cm | Standard 4×6 print | 1181 × 1772 px at 300 DPI |
| 13 × 18 cm | 5×7 print | 1535 × 2126 px at 300 DPI |
| 20 × 30 cm | 8×12 print, framed photo | 2362 × 3543 px at 300 DPI |
How to Use the CM Mode
Upload & Switch to CM
Upload your image, then click the cm button in the unit row above the width and height fields.
Enter CM Dimensions
Type the exact width and height in centimeters (e.g., 3.5 × 4.5 for a passport photo). Set DPI to 300 for print.
Resize & Download
Click resize. The tool outputs an image at the exact pixel dimensions matching your CM + DPI specification.
Understanding DPI and CM
DPI (Dots Per Inch) determines how many pixels map to one physical inch when printed. The formula for converting CM to pixels is:
pixels = cm × DPI ÷ 2.54 300 DPI — Standard for high-quality printing: passport photos, official documents, photo prints. This is what you should use for anything that will be physically printed.
150 DPI — Acceptable for casual prints, posters viewed from a distance.
72 DPI — Screen resolution. Use only for images displayed on websites or screens, not for print.
Resizing in Pixels vs Centimeters
Pixels are the resizer's default unit, so if your form quotes a pixel count you do not need this page at all — open the tool and type the numbers in. The reason both units exist is that forms are inconsistent about which one they print, not that they want different things. 413 × 531 px and 3.5 × 4.5 cm are the same file. Enter either and you get identical output, because the second is just the first expressed at 300 DPI.
Where DPI stops mattering
DPI is an instruction to a printer about how large to render each pixel. It answers "how many pixels is 3.5 cm?" — and once that question is answered, it has done its whole job. An upload portal reads pixel dimensions and file size and nothing else, so it never asks for a DPI and cannot tell what DPI produced your file.
That is why a form quoting centimeters is not asking you to print anything. It is quoting the size the photo would be on paper, because that is the tradition those forms inherited from over-the-counter applications, and then accepting a digital upload of it. Convert once at 300 DPI, check the pixel count, and stop thinking about DPI.
When You Need CM Sizing
🛂 Passport & Visa Photos
Most countries specify passport photo dimensions in CM: 3.5×4.5cm (India, UK, EU), 5.1×5.1cm (US), 3×4cm (Japan).
🪪 ID Cards & Documents
Employee ID photos, driving licenses and college forms — all commonly specify CM dimensions for the embedded photo.
🖨️ Professional Printing
Photo prints (10×15cm, 13×18cm, 20×30cm), business cards, brochures — printers work in physical measurements.
📝 Exam Applications
SSC, RRB, the state PSCs, JEE, NEET, GATE and the defence exams all specify photo size as "3.5×4.5 cm" rather than pixels — that is 413×531 px at 300 DPI. They differ on file size, though, from GATE's 5–200 KB down to SSC's 20–50 KB, so the India exam requirements page lists the band per exam. UPSC is the exception on both counts — it states a file size and face coverage but no dimensions.
Frequently Asked Questions
How do I resize an image to exact CM dimensions?
Open our image resizer, switch the unit to "cm" using the unit toggle, enter your desired width and height in centimeters, then click resize. The tool calculates the correct pixel dimensions based on your chosen DPI (default 300 DPI for print quality).
What DPI should I use when resizing in CM?
For printing (passport photos, documents, posters), use 300 DPI — this is the standard for sharp print output. For screen-only use (email, web upload), 72–96 DPI is sufficient and produces a smaller file size.
What is the relationship between CM and pixels?
The conversion depends on DPI (dots per inch). Formula: pixels = cm × DPI ÷ 2.54. For example, 3.5 cm at 300 DPI = 3.5 × 300 ÷ 2.54 = 413 pixels. Our tool does this calculation automatically when you select CM as the unit.
Can I resize an image to CM for a passport photo?
Yes. Select CM as the unit, enter 3.5 × 4.5 cm (standard for India, UK, and Schengen visa), and set DPI to 300. The tool will resize your image to exactly 413 × 531 pixels, which is the correct pixel equivalent for printing at passport photo size.
How is CM different from inches for image resizing?
1 inch = 2.54 cm. Both are physical measurement units used for print. Most of the world uses CM (metric), while the US primarily uses inches. Our tool supports both units — simply toggle between them. A 5.1 × 5.1 cm photo is the same as 2 × 2 inches.
Why does my resized image look blurry when printed?
This happens when the source image has too few pixels for the print size. For a sharp 3.5 × 4.5 cm print at 300 DPI, you need at least 413 × 531 pixels in the original. If your source image is smaller, the tool must upscale it, which reduces sharpness. Always start with the highest resolution source available.
Can I resize in mm instead of cm?
Yes — the resizer has a dedicated mm unit button, so enter 35×45 directly with mm selected. There is no need to convert anything. If you prefer working in centimeters, dividing by 10 gives the same pixel output (35×45 mm = 3.5×4.5 cm), and decimal values are accepted so nothing gets rounded.
How do I resize an image in pixels instead of cm?
Pixels are the resizer's default unit — open it, leave the unit set to px and type the width and height straight in. You only need the cm mode when your form states a physical size, and the two are not different requirements: a form asking for 413 × 531 pixels and a form asking for 3.5 × 4.5 cm want the same file, because 413 × 531 is 3.5 × 4.5 cm at 300 DPI. Whichever unit you enter, the output file is identical.
Does DPI change the file when I upload it to a portal?
No. DPI is only a scaling instruction for a printer, and it has no effect on an upload — a portal reads pixel dimensions and file size, and nothing else. So DPI matters when you are asking us "how many pixels is 3.5 cm?" and stops mattering the moment the file is sized. Two files of the same pixel dimensions are the same upload regardless of what DPI produced them, which is why an upload form never asks for one.
What cm size is an A4 page?
An A4 page measures 21.0 × 29.7 cm. At 300 DPI (print quality), that equals 2480 × 3508 pixels. If you're preparing a full-page image for print, resize to these dimensions. For other standard sizes: A5 is 14.8 × 21.0 cm, A3 is 29.7 × 42.0 cm, and Letter (US) is 21.6 × 27.9 cm.
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