How to change the DPI of an image
- Enter the Resolution you need, from 72 to 1200 dpi. The default is 300.
- Select Choose files and add your JPG or PNG images.
- Select Download. The file name ends with the new value, for example photo-300dpi.jpg.
What DPI means
DPI means dots per inch. It is a label stored in the image file that says how many pixels fit in one inch when printed. A picture of 1800 by 1200 pixels at 300 dpi prints at 6 by 4 inches. The same picture labelled 72 dpi would print at 25 by 16.7 inches, but with the same pixels, so it looks coarser. The label does not change how many pixels there are.
How this tool works
Most online tools redraw the image to change DPI, which costs quality. This tool does not. For a JPG it edits the density fields of the JFIF header, or adds a header if the file has none. For a PNG it writes a pHYs chunk with the right checksum, in pixels per metre. The picture data is copied byte for byte, so the result is identical and has the same quality.
When you need it
Some forms and print shops ask for a 300 dpi image. Some scanners save at 72 dpi or 96 dpi even though the picture has plenty of pixels. Changing the label lets a layout program place the image at the right physical size. It does not resize the image. If a form wants specific pixel dimensions, use the image resizer.
Tips
- For passport and ID photos, set the size first with passport photo size, then set 300 dpi.
- Check what a file contains first with the metadata viewer.
- Make files smaller with the image compressor.
Only JPG and PNG files are supported, since those are the formats where the label can be edited without re-encoding. Everything runs on your device, and your files are never uploaded.