Resize an image in cm or mm
Type the width and height in centimetres or millimetres and the tool works out the pixels at 300 DPI, so 10 x 15 cm becomes 1181 x 1772 pixels. It saves 300 DPI in the file, so the photo prints at the size you typed. Change the DPI and the centimetres stay put.
Jump to the toolYour workspace PIXELS · PREVIEW · DOWNLOADPrivate by default
That is 0 x 0 pixels at 300 DPI.
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How many pixels is a centimetre?
It depends on the DPI, the number of pixels printed per inch. An inch is 2.54 cm, so divide the centimetres by 2.54 and multiply by the DPI.
| DPI | Pixels in 1 cm | Pixels in 10 cm |
|---|---|---|
| 72 DPI | 28.35 | 283 |
| 96 DPI | 37.80 | 378 |
| 150 DPI | 59.06 | 591 |
| 200 DPI | 78.74 | 787 |
| 300 DPI | 118.11 | 1181 |
| 600 DPI | 236.22 | 2362 |
A millimetre is a tenth of those. At 300 DPI, 1 mm is 11.81 pixels, which is why the tool rounds to whole pixels and shows you the result under the fields.
How large can your photo print?
As large as its pixels allow at the DPI you pick. Beyond that the tool has to enlarge the photo, which adds pixels by blending neighbours and makes the print softer.
| Photo | At 300 DPI | At 150 DPI |
|---|---|---|
| 12 MP phone photo, 4000 x 3000 | 33.87 x 25.4 cm | 67.73 x 50.8 cm |
| Full HD, 1920 x 1080 | 16.26 x 9.14 cm | 32.51 x 18.29 cm |
| Square post, 1080 x 1080 | 9.14 x 9.14 cm | 18.29 x 18.29 cm |
Open your own photo and the fields show its size in centimetres at the current DPI. That is its largest sharp print. Type a larger size and the pixel line under the fields shows how much it grew.
Why the DPI has to be in the file
A centimetre only means something on paper. The file holds pixels plus one number, its DPI, that tells a printer how many to fit into each inch.
Without it, or with a different one, the same pixels print at a different size. A photo sized for 10 cm at 300 DPI but marked 72 prints 41.66 cm wide.
So this tool saves the DPI in every JPEG and PNG it makes. WebP and AVIF have no field for it; save as JPEG or PNG for print.
What happens to the shape?
With the lock closed, type one side and the other follows your photo's own shape, so nothing is cut off.
Open the lock to set both sides, and the tool fills that size and crops the overflow evenly from the centre. It never stretches.
Sizes with their own page
Common print sizes in millimetres or centimetres, each on a page that opens at that size:
What happens to your photo?
Your selected photo is processed in your browser, without an image upload to a server. The page may download code and codecs needed for editing.
Save your result before closing the tab; unsaved edits are kept in memory rather than in an online account.
Common questions
How do I convert cm to pixels?
Divide by 2.54 and multiply by the DPI. At 300 DPI, 10 cm is 10 / 2.54 x 300, which rounds to 1181 pixels. The tool does this as you type and shows the pixels under the fields.
What DPI should I use?
300 for a photo print, which is where the tool starts. A form or print shop that names a DPI wins; type it beside the size fields and the centimetres stay the same.
Why does my image print at the wrong size?
Usually because the file says a different DPI than the one it was sized for, or none, and the printer assumed one. Also check the print dialog is set to actual size, not fit to page.
Can I resize in millimetres instead?
Yes. Switch the fields from cm to mm. The two describe the same size, so switching changes the numbers you see and not the image.
Does resizing in cm reduce quality?
Making the photo smaller throws away pixels, and saving as JPEG re-encodes it; keep the quality slider high for print. Making it larger than the photo's own pixels allow makes it softer.
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