How to Change an Image to 300 DPI

What actually changes

DPI (dots per inch) is a note inside the image file about how large it should be printed. In Change DPI:

• JPG: the tool edits the header, and the EXIF resolution tags too if the file has them.
• PNG: it writes the pixel-density chunk.
• The picture data isn’t touched. Same pixels, same quality, now labelled with the DPI you chose.

It then reads the DPI back from the finished file to confirm it took.

Steps

1. Open Change DPI and add the image.
2. Choose 72, 96, 150, 200 or 300, or type your own. (200 DPI works exactly the same way as 300.)
3. Download the result. Check the confirmation of the DPI read back from the file.

Formats that can’t hold a DPI

WebP, GIF, BMP and AVIF have no standard DPI field. If you add one of those, leave “convert to JPG” on and the tool re-saves it as a high-quality JPG first, then writes the DPI. That is a re-save, so the file isn’t pixel-identical to the original; it’s a high-quality JPG.

If two programs show different DPI

Some programs read the EXIF tags and some read the JPEG header. WillItUpload updates both when both exist, so they agree.

If the form also fixes the pixel size

DPI doesn’t change the pixels. If a portal wants “300 DPI and 413 × 531 pixels”, you need both:

1. Set the pixel size and file size with KB + Dimensions. Under Advanced you can add a DPI for JPG, which is written into the file and re-checked.
2. Or paste all the rules into Fix Upload File and let it do everything together.

Then check the file with the Image Requirement Checker. If the file carries no DPI at all, the checker shows “Not set in file”. A required DPI rule is not a pass until a value is written, and the fixer writes one.

What it doesn’t do

• It doesn’t sharpen the picture or add detail. See 72 DPI vs 300 DPI.
• It doesn’t change the pixel dimensions. For the relationship between the two, see DPI vs pixel dimensions.