Image DPI changer
Choose a JPG or PNG, type the DPI you need, such as 300 for print, and download the file. Only a few metadata bytes are rewritten, so the pixels are not re-encoded and the picture is not resampled. Nothing leaves your device.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose or drop a JPG or PNG file.
- Type the DPI or press one of the presets (72, 96, 150, 300, 600).
- Check the print size shown below and press Download with new DPI.
How it works
DPI is a note in the file about how many pixels fit in an inch when printed. A PNG stores it in a pHYs chunk as pixels per metre: the tool converts dots per inch by dividing by 0.0254, so 300 DPI is 11811 pixels per metre. A JPG stores it in the JFIF header as dots per inch directly, and many cameras also write it in the Exif data; both are updated. If a JPG has no JFIF header, a small one is added after the start of the file.
Example
A phone photo of 4000 × 3000 pixels set to 300 DPI prints at 13.33 × 10 in (33.9 × 25.4 cm). The same file set to 72 DPI is 55.6 × 41.7 in. The pixels are identical in both files.
Tips
- Print services usually ask for 300 DPI at the final print size. If the picture has too few pixels, a higher DPI will not fix that.
- To change the number of pixels, use the image resizer instead.
Frequently asked questions
Does changing DPI change the quality or the pixels?
No. The tool copies the file and rewrites only the resolution fields. In a PNG it replaces the pHYs chunk, in a JPG the JFIF density and, when present, the Exif resolution tags. The compressed pixel data is copied byte for byte.
Will my picture get sharper at 300 DPI?
No. A 1500 × 1000 pixel picture has the same pixels at 72 and at 300 DPI. A higher DPI only makes the intended print size smaller: 1500 pixels at 300 DPI is 5 inches wide, at 72 DPI it is about 20.8 inches.
Why does the current resolution say "not set"?
Many files carry no resolution, or only an aspect ratio instead of dots per inch. Many programs then assume 72 or 96 DPI. After you download, the file has the DPI you chose.
What about WebP, GIF or HEIC?
They are not supported here. Convert the picture to JPG or PNG first with the image converter, then set the DPI.