Free tool
Change Image DPI Without Touching the Pixels, or Resample to a Print Size
A print shop or a form asks for a picture at 300 DPI, and yours says 72. This page changes that number in the file itself, and shows what size the picture will print at. If the pixels are not enough, a second mode resamples the picture to a paper size you pick.
| At | In inches | In centimetres |
|---|
DPI
The DPI is written in the JPG or PNG header, and into the EXIF and Photoshop notes when the file has them. HEIC, WebP and other types are not supported, as they have no DPI in the same way.
Your pictures are read and changed in your browser and are never uploaded. The last DPI, mode, paper size and quality you chose are kept on your own device, but your pictures are not.
What the DPI request really means
When someone asks for a file at 300 DPI, they usually mean the file should print at a given size with enough detail. DPI is only a label stored in the file, telling a printer or a layout program how many pixels to place in each inch. The pixel grid is what holds the detail. A picture of 2400 by 3000 pixels prints at 8 by 10 inches at 300 DPI, and the same picture marked 600 DPI prints at 4 by 5 inches. Nothing about the picture changed, only the label.
That is the first mode, called Keep the pixels. It rewrites the density fields and leaves every other byte as it was. The page tells you how many bytes changed, so you can see the edit was tiny.
Keep the pixels or resample
| Keep the pixels | Resample | |
|---|---|---|
| What changes | Only the stored DPI | The picture is redrawn at a print size |
| Pixel count | Same as the original | Becomes the paper size times the DPI |
| Colour profile | Left as it was | Kept and saved again |
| Best for | A form or print shop that checks the DPI number | A picture that must fit an exact sheet |
| Quality loss | None | Possible if the picture is enlarged |
In resample mode you pick the sheet from a list, which includes 4 by 6, 5 by 7, 8 by 10 and 11 by 14 inches, US Letter, and A6, A5, A4 and A3, or type your own size in inches, centimetres or millimetres. The shape setting either fills the sheet and crops the edges, or keeps the whole picture. The sheet is turned to match your picture, so a wide picture gets a wide sheet. JPG results have a quality slider.
Where the DPI is written
- JPG: in the JFIF density fields. A file without a JFIF header is given one at the front. If the file already carries EXIF resolution tags or a Photoshop resolution block, those are changed too, so no program reads an old number from them.
- PNG: in the pHYs chunk, stored as pixels per metre, which is the DPI divided by 0.0254 and rounded.
- Not supported: HEIC, WebP and other types. Convert them to JPG or PNG first.
The DPI buttons offer 72, 150, 300 and 600, and you can type your own value. A line above the pictures shows the print size at the current DPI, in inches or centimetres, which is the quickest check that the number fits your job.
Mistakes that waste time
- Expecting a DPI change to add detail. A small picture marked 300 DPI is still small, and it simply prints smaller.
- Raising the DPI to a huge number to look sharp. The printed size shrinks in step, so check it first.
- Using resample on a picture that is already the right size, which only adds a pass of resizing.
- Forgetting that screens ignore the label. A web page shows the picture by its pixels, so changing DPI does not make a site load faster or look sharper.
For web images, resize or compress instead. Our guide to website speed optimization for small sites explains why file weight matters more than the DPI label online.
Frequently asked questions
Does changing DPI change the picture quality?
In the keep the pixels mode, no. Only the stored number changes and the pixels are untouched. In resample mode the picture is redrawn, so enlarging can soften it.
Can I change the DPI of many pictures at once?
Yes. Add several files, set the DPI once, and download them together in a ZIP, or save each one on its own.
Which file types work?
JPG and PNG. HEIC, WebP and other types are not supported, so convert them to JPG or PNG before using this page.
Why does my picture still look the same size on screen?
Screens use the pixel count, not the DPI label. The label matters when you print or place the file in a layout program.
What DPI should I choose for print?
Ask the printer, since the right value depends on the job. The page offers 72, 150, 300 and 600 as one-click choices and shows the print size for whichever you use.
Are my pictures uploaded?
No. They are changed in your browser and stay on your computer.
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