Resize Image in cm
Forms and print shops describe photos in centimeters, but image files are measured in pixels. Type the size in cm here, pick the DPI, and the tool works out the pixel dimensions, crops to the shape and writes the DPI into the file.
Resize Image
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Applies when both sides are set or the shape changes. Fit inside keeps everything and may come out smaller on one side; crop fills the frame exactly; pad adds borders; stretch distorts.
Which part of the image is kept when cropping. Smart keeps the busiest area, usually a face or the main subject.
Color of the borders added around the image, e.g. #FFFFFF for white.
Pixels per inch used to turn cm, mm or inches into pixels and written into the file. 300 is standard for print, 200 for most online forms.
Same as input keeps the original format. Pick GIF or WebP to keep an animation, PNG for transparency.
Applies to JPG, WebP and AVIF. 85 looks identical to the original for photos.
Quality is lowered until the resized file is at or just under this size.
How to use this tool
- 1
Upload the image
Add a photo, scan or signature in JPG, PNG, HEIC, WebP or another common format.
- 2
Type the size in centimeters
The page opens with Unit on cm and 3.5 × 4.5 cm filled in, a common photo size on application forms. Change Width and Height to the numbers you were given; decimals like 2.54 are fine.
- 3
Check DPI, then resize
DPI starts at 300, the print standard. Use the value the form or print shop states, then press Resize and download the result.
A centimeter size only becomes a pixel size once you choose a DPI. Set both here and the tool does the arithmetic: 3.5 cm at 300 DPI is 413 px, at 200 DPI it is 276 px.
How to resize an image in cm, step by step
A digital photo has no physical size of its own. It is a grid of pixels plus a small number stored in the file, the DPI (dots per inch, also called PPI), which tells printers and layout programs how many of those pixels belong in one inch of paper. Change that number and the same file prints larger or smaller. That is why a request such as "photo 3.5 × 4.5 cm" is incomplete until you know the DPI, and why this page asks for both.
The math is short. One inch is defined as exactly 2.54 cm, so a length in centimeters is divided by 2.54 to get inches and then multiplied by the DPI to get pixels. For 3.5 × 4.5 cm at 300 DPI: 3.5 ÷ 2.54 × 300 = 413 px wide, 4.5 ÷ 2.54 × 300 = 531 px tall. The table runs the same calculation for common lengths.
Centimeters to pixels at 72, 150 and 300 DPI
| cm | Pixels at | ||
|---|---|---|---|
| 72 DPI | 150 DPI | 300 DPI | |
| 2 | 57 | 118 | 236 |
| 3.5 | 99 | 207 | 413 |
| 5 | 142 | 295 | 591 |
| 6 | 170 | 354 | 709 |
| 15 | 425 | 886 | 1772 |
| 21 (A4 width) | 595 | 1240 | 2480 |
| 29.7 (A4 height) | 842 | 1754 | 3508 |
What happens to the file when you resize by cm
Centimeters become pixels
Width and height in cm are multiplied out with the DPI you chose, for example 3.5 × 4.5 cm at 300 DPI gives 413 × 531 px.
The image is fitted to the shape
With Crop to fill the photo is scaled to cover the new frame and trimmed; Pad with color keeps all of it and adds borders instead.
The DPI is written into the file
Word, Photoshop and photo printers read the tag and place the image at the centimeter size you typed.
Common sizes people resize to in centimeters
The 3.5 × 4.5 cm default matches the photo size used for UK passports (35 × 45 mm on GOV.UK), Schengen visa applications and many Indian exam and recruitment forms, which usually pair it with a KB limit. A US passport photo is 2 × 2 inches, which is 5.08 × 5.08 cm; enter it in inches to avoid rounding. For photo prints, 10 × 15 cm is the standard postcard-sized print, which needs 1181 × 1772 px at 300 DPI.
Two warnings save most failed uploads. First, resizing to centimeters can only lower or keep the detail you have: a 300 × 400 px phone crop stretched to 10 × 15 cm at 300 DPI will look soft no matter what number is written in the file, so tick Never enlarge if you prefer the original pixels. Second, a form that gives both cm and KB needs both handled; combine this page with Limit file size, or read our walkthrough on passport size photo in cm, inches and pixels for the full routine.
Resizing images in centimeters: FAQ
How many pixels is 1 cm?
It depends entirely on the DPI. At 300 DPI, 1 cm is 118 px; at 150 DPI it is 59 px; at 72 DPI it is 28 px. The formula is pixels = cm ÷ 2.54 × DPI, because one inch is exactly 2.54 cm.
How do I resize a photo to 3.5 × 4.5 cm?
Leave the defaults on this page: width 3.5, height 4.5, unit cm, DPI 300. The result is 413 × 531 px with the DPI tag set to 300, which prints at exactly 3.5 × 4.5 cm. If the form also limits the file size, tick Limit file size under Advanced settings and enter the KB value.
Which DPI should I choose for an online form?
Use the DPI the form states. If it states only centimeters, 200 to 300 DPI is safe for photos and signatures. A lower DPI gives fewer pixels and a smaller file, which helps with strict KB caps, but below 150 DPI a face starts to look soft when printed.
Why does my image still show the old size in centimeters?
Some viewers ignore the DPI tag and assume 72 or 96 DPI, so they report a different physical size even though the file is correct. Check the pixel dimensions instead: 3.5 × 4.5 cm at 300 DPI should read 413 × 531 px.
Can I enter the size in millimeters or inches instead?
Yes, Unit also offers mm and in, and the conversion uses the same DPI. For a size given in millimeters, resize image in mm starts with that unit selected.
Will the picture be stretched to fit the new size?
No. Fit is set to Crop to fill, so the image is scaled until it covers the new shape and the overflow is trimmed, with Crop position on Smart to keep the face in frame. Choose Stretch to exact size only if distortion does not matter.
Other resize tools
- 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.
- 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.
- Resize Image to 600 × 600 PixelsCrop and resize any photo to exactly 600 × 600 pixels, the minimum for US visa photos and a 2 × 2 in print at 300 DPI. Subject kept centered, JPG output.
- Resize Image to 300 × 300 PixelsMake any photo exactly 300 × 300 px: square crop around the subject, no stretching, original format kept. For thumbnails, avatars and web forms, 20 at once.
- Change the Aspect Ratio of an ImageChange a photo's aspect ratio without typing pixels: pick 1:1, 4:5, 16:9, 9:16, 3:2 or 21:9, then crop around the subject or pad with a color.
- Pixel to CM ConverterConvert pixels to centimeters, inches or millimeters at 72, 96, 150 or 300 DPI, and MB to KB with the 1024 or 1000 rule. Formulas and tables included.
