PandaFileKit

Change image DPI

Write a new DPI into JPG and PNG files. The pixels stay exactly as they are.

JPG · PNG · WEBP · HEIC → JPG / PNG

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Counted with the browser's Performance API during the last job. It sees every request the page makes, but not what is inside them, so anything that is not a static download is counted above.

To check yourself: open DevTools → Network, clear the list, run the tool, and inspect each request. None will contain your file. You can also switch to offline after the page loads; tools whose engine is already downloaded keep working.

Drop images here

or paste, or choose files

JPG · PNG · WEBP · HEIC → JPG / PNG

Add one or more JPG or PNG files.

Specific jobsChange DPI to 300

Set the DPI a form or print shop asks for

DPI (dots per inch) is a number stored in an image file that tells printers how large to print it. Cameras and phones often write 72 or 96, and some upload forms, print shops and publishers reject anything not marked 300 DPI even when the photo has plenty of pixels. Change image DPI rewrites that number and leaves the picture alone.

  • A portal or publisher that rejects a photo because it reports 72 DPI.
  • Preparing images for a print shop, book or magazine that asks for 300 DPI.
  • Making a batch of scans all report the same DPI.

Pick a DPI; JPG and PNG are edited in place

Choose 72, 96, 150, 300 or 600, or type any value from 1 to 2400. For JPG the JFIF density is rewritten and, when the file has EXIF data, the EXIF resolution too, so Windows, macOS and editors all read the same value. For PNG the pHYs chunk is replaced or added. The compressed image data is left byte for byte as it was, so there is no quality loss and the file size changes by only a few bytes. WebP can't store DPI, so WebP files are saved as PNG, and iPhone HEIC photos are converted to JPG, each carrying the new DPI.

  • Batches get the same DPI on every file.
  • Need a print size such as 3.5 × 4.5 cm as well? Use Resize image in cm, mm or inches, which changes the pixels.

DPI doesn't add detail

Changing the DPI doesn't add or remove pixels, so it can't sharpen a small or blurry photo. A 600 × 600 px image marked 300 DPI prints at 2 × 2 inches; marked 72 DPI, the same pixels print at about 8.3 × 8.3 inches. If a printer needs 300 DPI at a given size, the image needs at least that size in inches × 300 pixels.

  • Check the new value in file properties (Windows: Properties → Details; macOS Preview: Tools → Show Inspector).
  • If a form also gives pixel dimensions, check those separately with Image dimensions.

Change image DPI: questions

Does changing DPI reduce quality?

No, not for JPG and PNG. Only the resolution fields in the header are rewritten; the compressed image data is untouched.

Will 300 DPI make my photo sharper?

No. DPI only tells a printer how many pixels to put in an inch. The number of pixels, and so the detail, stays the same. To print sharply at a size, the image needs enough pixels for it.

Why is the file size almost the same?

Because only a few header bytes changed. A tool that makes the file much larger or smaller has re-encoded the picture.

What happens with WebP and HEIC files?

WebP can't store DPI, so it's saved as PNG; HEIC is converted to JPG. Both are re-encoded once and carry the new DPI.

Can I change the DPI of many images at once?

Yes. Add a batch; every file gets the same DPI.

Is the image uploaded?

No. The header is rewritten in your browser.