Change Image DPI

No. Changing DPI cannot improve quality, and this tool does not pretend otherwise.

What it does is edit a small piece of metadata — the pHYs chunk in a PNG, the JFIF density fields in a JPG — and leave the image exactly as it was. Camera details such as GPS location are dropped on the way, as they are by every tool here; the photo's orientation is kept. The compressed image data is copied across untouched, which means:

• No re-encoding, so a JPG does not go through another generation of compression.
• No resampling, so nothing is softened or sharpened.
• Identical pixels. Open the before and after side by side and they are the same image.

That is a genuine advantage over doing this in an image editor, where opening and re-saving a JPG costs a little quality every time.

If quality is the real problem

Work out whether you have enough pixels for your printed size:

• You do — set the DPI here and you are finished.
• You do not — you need a larger original. Enlarging raises the pixel count without adding detail, so the result is a bigger soft image. It will satisfy a checker and disappoint a printer.

The tool shows the printed size before and after precisely so you can see this. If 300 DPI gives you a print smaller than you need, that is the answer: the file is too small, and no setting changes it.

Which DPI to choose

• 300 — the standard for photographic printing, magazines and most professional work. Use this unless told otherwise.
• 150 — acceptable for large posters and banners viewed from a distance, where the eye cannot resolve fine detail anyway.
• 600 — line art, technical drawings and text-heavy scans, where crisp edges matter more than tonal detail.
• 72 or 96 — historical screen conventions. Still requested by some systems, though meaningless for actual screen display.

Where the requirement comes from

• Print shops and photo labs, which specify 300 DPI at the finished size.
• Publishers and magazines, whose submission guidelines almost always name it.
• Academic and conference submissions for figures and diagrams.
• Visa, passport and official application portals, some of which check the field automatically.
• Print-on-demand services, which reject uploads below a threshold.

Where a checker reads the field, setting it is genuinely all that is needed. Where a human looks at the result, having enough pixels is what matters — and the two are often confused in the same set of instructions.

Working out what you need

Multiply the printed size by the DPI:

• A5 (5.8 × 8.3 in) at 300 DPI → 1740 × 2490 px
• A4 (8.3 × 11.7 in) at 300 DPI → 2490 × 3510 px
• 6 × 4 in photo at 300 DPI → 1800 × 1200 px
• Passport photo 35 × 45 mm at 300 DPI → 413 × 531 px

Compare those with your actual pixel dimensions, which are shown when you add a file. If yours are larger, you have room to spare. If smaller, the print will be softer than the specification intends.

Why an editor is not needed for this

Opening a JPG in an image editor to change its DPI means decoding and re-encoding it, which costs a little quality every time — for a change that touches no pixels at all. Editing the metadata directly avoids that entirely.

It also avoids a common trap: some editors offer to resample when you change the resolution, which quietly changes the pixel dimensions too. That is a different operation, and if you want it, resizing is the honest way to do it.

Only the header changes

Your file is uploaded, and a handful of bytes in its header are rewritten on our server. The image data passes through untouched — the file you download differs from the one you added only in its header: the new DPI, and no camera details.