How to Change Image DPI to 300 Without Resizing the Pixels
A form or print shop wants 300 DPI and your file says 72. Changing the label takes seconds and leaves every pixel as it was, as long as you understand what DPI is and is not.
Add a JPG or PNG, choose a DPI and download. The pixels are not changed.
What changing DPI does, and what it does not
DPI means dots per inch. For an image file it is a label that tells print software how large to make each pixel on paper. A 3000 x 2000 pixel image labelled 300 DPI prints at 10 x 6.67 inches. Labelled 150 DPI, the same pixels print at 20 x 13.3 inches. The pixels are identical, only the label differs.
This is exactly what the tool does. It writes the new DPI into the file and leaves the pixels alone, so width and height in pixels stay the same, the picture is not resampled and its quality does not change. It does not make an image sharper. A photo that has too few pixels for a large print will still look soft at 300 DPI.
Set the DPI in four steps
- Open Change DPI and add a JPG or PNG file with Select Image. WebP and other formats are not supported for this tool.
- Choose New DPI: 72 (screen), 96 (screen), 150 (print), 300 (print, the default), 600 (high-res print) or Custom. Custom takes any value from 1 to 2400.
- Press Apply DPI. The result line reads, for example, "DPI set to 300. File size: 2.1 MB (was 2.1 MB)."
- Press Download Image.
The file size barely changes because only a small header is edited, not the image data.
Do the pixel maths before you pick a number
Print size in inches is pixels divided by DPI. A form asking for "300 DPI" usually really means enough pixels for the printed size. Work it out:
| Image | At 300 DPI prints | At 150 DPI prints |
|---|---|---|
| 1200 x 1800 px | 4 x 6 in | 8 x 12 in |
| 2400 x 3000 px | 8 x 10 in | 16 x 20 in |
| 3000 x 2000 px | 10 x 6.7 in | 20 x 13.3 in |
If the pixel count is too low for the size and DPI you need, relabelling will not help: you need more pixels, ideally from a better original. Enlarging in a browser only smooths what is there, as noted in resizing without Photoshop.
Which DPI for which purpose
| Purpose | Common choice | Comment |
|---|---|---|
| Photo prints, flyers, brochures | 300 | The usual target for sharp printing at close range |
| Large posters viewed from a distance | 150 or less | Fewer pixels needed because the viewer is far away |
| Documents and forms for screens | 72 or 96 | The number rarely matters on screen |
| Fine line art or scans for archiving | 600 | Only useful if the source really has that many pixels |
These are conventions, not rules. A printer or a form states the numbers that apply to you, so follow those over any general table.
A worked example
A designer sends a 2480 x 3508 pixel image labelled 72 DPI, which shows as a poster of 34 x 49 inches in some programs. That pixel size is an A4 page at 300 DPI, since A4 is 8.27 x 11.69 inches and 8.27 x 300 is about 2480. Setting the DPI to 300 makes it open as a normal A4 page without changing a single pixel. If you instead needed A3 at 300 DPI, you would need roughly 3508 x 4961 pixels, and relabelling the A4-sized file would only print it at A3 with 212 pixels per inch. That may look acceptable from a distance or poor up close.
When changing DPI is the right fix
- A print shop or form checks the DPI value in the file and reads 72.
- An editor opens the image at an unexpected physical size because the label is wrong.
- You have a scan or screenshot that is already high resolution and only needs a correct tag.
When it will not do what you hoped
- The requirement is about pixels. "At least 600 x 600 pixels" is not a DPI request. Check with Image Size Checker.
- A program still shows the old value. JPG files can carry resolution information in more than one place, and some programs read a different place from the one this tool updates. PNG stores it in its own chunk.
- Web use. Browsers ignore DPI for layout, so for a website it makes no difference. Dimensions matter.
- You need to shrink the file. DPI will not do it. Use Compress JPG or resize.
Check the result before sending it to print
After downloading, open the file's properties on your computer and look for the resolution or DPI field, or open it in the print program and see what physical size it reports. Compare that with the size you want. If the numbers match, you are done. If the program shows something else, ask the printer which value they read, since some tools look at a different field from the one this page edits.
Related print preparation
To get the pixel size right first, use Resize Image. For cropping to a print ratio, see cropping to exact pixels. The change happens in your browser and the file is not uploaded.
Frequently Asked Questions
Does changing DPI change the pixel size?
No. Width and height in pixels stay exactly the same. Only the print resolution label in the file changes.
Will it make a low-resolution image look sharper?
No. A photo with too few pixels still prints soft at 300 DPI. You need more pixels from a better original.
Which formats and values are supported?
JPG and PNG. Choose 72, 96, 150, 300 or 600, or a custom value from 1 to 2400.
Why does the file size hardly change?
Only a small piece of header data is edited. The image data is not recompressed.
Does DPI matter for websites?
Browsers ignore it for layout. Pixel dimensions are what count on screen.
Why does another program still show the old DPI?
Some programs read resolution from a different part of the file than the one this tool updates.