Calculator
What the Image DPI Changer does
Image DPI Changer: writes the resolution tag (a PNG pHYs chunk or the JPEG JFIF density) so print software sizes the picture correctly. Everything runs in your browser and the file is never uploaded.
The Image DPI Changer works on a file you choose, without sending it anywhere. Everything runs on your own device, which means no waiting and no copy left on a server.
A smaller file that still looks right is usually only a few settings away. That is usually what brings people preparing images for the web here.
The page holds your values in memory and forgets them the moment you close it.
The meaning of each field, the formula in use, and a worked example that starts from the default inputs are all further down.
What do the Image DPI Changer fields mean?
The Image DPI Changer uses 5 inputs. A complete set of starting values is loaded for you, so nothing is required before the first result appears.
| Field | What to enter | Default |
|---|---|---|
| Image file | stays on your device | none |
| DPI | choose from 300 (print), 150, 96 (Windows screen), 72 (classic screen), 600 (fine print) or Custom | 300 (print) |
| Custom DPI | accepts 1 to 9600 | 240 |
| Export as | choose from PNG or JPEG | PNG |
| Quality % | accepts 10 to 100 | 92 |
How does the Image DPI Changer work?
Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same calculation.
The guard clauses run before the formula does, which is why mistakes surface next to the field.
What a typical run looks like
You provide: Image file, DPI, Custom DPI, Export as and Quality %
What happens: the file is read into memory by your browser, processed locally, and offered back as a download. It is never uploaded.
You get back: a processed file plus a short status summary in the tool panel.
The tab does the processing, so speed tracks your hardware and very large files fail on memory rather than on a quota.
How to use it
- Choose your file under Image file, or drag it onto the drop area.
- Pick a value for DPI: the options are 300 (print), 150, 96 (Windows screen), 72 (classic screen), 600 (fine print) or Custom.
- Put Custom DPI (1 to 9600).
- Pick a value for Export as: the options are PNG or JPEG.
- Fill in Quality % (10 to 100).
- Press Set DPI.
- You get Status back.
- Share the link rather than a screenshot. It carries the values with it.
What this tool does not do
- EXIF metadata may be dropped during processing, which is usually desirable but is worth knowing.
- Re-encoding a lossy format such as JPEG always loses some detail, even at maximum quality.
- It assumes the values you give are already consistent with each other.
- It validates ranges, not intent. A value can be accepted and still be the wrong one to use.
- Performance scales with your own hardware, since no server does the work.
Frequently asked questions
Image file, DPI, Custom DPI, Export as and Quality %. That is the whole form. Each field is pre-filled with a sensible default, meaning you can explore the calculation before committing to real figures.
Custom DPI accepts 1 to 9600. Out-of-range entries are refused up front, which is safer than silently clamping them.
It is not uploaded. Everything happens on your device, so no copy of your file exists on any server.
It is free to use, with no premium tier holding back the useful parts.
Reliable for the case described. Where more than one convention exists, the method section says which one is used.