Change Image DPI
Set the DPI value stored in your image, or work backwards from a physical print size to the pixels you need. Both modes run locally, and the tool is honest about which one actually changes your picture.
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Images are processed on your device and never uploaded.
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Runs on your device — nothing is uploaded.
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The thing nobody explains about DPI
Changing DPI metadata does not change the number of pixels in your image. DPI is a note attached to the file saying "when printed, lay these pixels down at this density". The pixels themselves are identical before and after.
A 1200×1800 image is 1200×1800 whether it is tagged 72 DPI or 300 DPI. What changes is the printed size:
- at 300 DPI it prints at 4 × 6 inches;
- at 150 DPI the same pixels print at 8 × 12 inches, half as sharp;
- at 72 DPI they print at roughly 16.7 × 25 inches, and look it.
So if a print shop asks for "300 DPI", what they need is enough pixels for your print size at 300 DPI. Re-tagging a small image as 300 DPI satisfies the letter of the request and produces a small, blurry print.
Mode 1 — change the DPI metadata only
Pixel dimensions are left exactly as they are; only the density value written
into the file changes. The JFIF density fields are rewritten for JPEG and the
pHYs chunk for PNG, without re-encoding the image data — so this mode
is completely lossless.
Use it when software or a submission portal insists on a specific DPI tag and your pixel dimensions are already correct.
Mode 2 — resize for a physical size
Enter the physical size you want to print and the DPI, and the tool computes and applies the pixel dimensions:
4 × 6 inches at 300 DPI → 1200 × 1800 pixels A4 (8.27 × 11.69 in) at 300 DPI → 2480 × 3508 pixels 2 × 2 inches at 300 DPI → 600 × 600 pixels
The image is resampled to those dimensions and tagged with the DPI, so the file is genuinely correct for the print rather than merely labelled correctly.
Which DPI do I need?
| DPI | Use |
|---|---|
| 72 / 96 | Screen-only. The historical web default; meaningless for print. |
| 150 | Draft prints, posters viewed from a distance. |
| 200 | Some document and ID scanning requirements. |
| 300 | The standard for photo prints, passport photos and commercial printing. |
| 600 | Line art, text scans and fine detail where edges must stay crisp. |
Frequently asked questions
Are my images uploaded to your server?
No. The image is decoded, processed and re-encoded by your own browser using the Canvas and Web Worker APIs. There is no upload endpoint for this tool — open your browser's network panel while you use it and you will see no request carrying image data.
Does changing DPI improve image quality?
No. In metadata-only mode nothing about the picture changes at all. Quality for printing comes from having enough pixels, which is what the physical-size mode gives you.
What is the difference between DPI and PPI?
PPI (pixels per inch) describes a digital image; DPI (dots per inch) describes a printer's ink dots. In everyday use — and in image file metadata — the two terms are used interchangeably.
Which formats support a DPI tag?
JPEG stores it in the JFIF header and PNG in the pHYs chunk; both are handled here. WebP has no standard density field, so exporting to WebP drops the tag.
What happens to my file when I close the tab?
It is gone. The image only ever exists in your browser's memory as an object URL; closing or refreshing the page discards it. Nothing is written to our servers, and nothing is stored on your device unless you download the result.