Last updated:
What DPI actually is
DPI (dots per inch) is a number that tells software how large an image should be printed. It is a small tag stored alongside the pixels, nothing more. A photo 3000 pixels wide tagged 72 DPI says "print me 105 cm wide"; the same photo tagged 300 DPI says "print me 25 cm wide".
The part that matters: the pixel count is identical in both cases. The only thing that changed is the file’s claim about its own physical size.
What "make it 300 DPI" really means
Print shops, journals and some marketplaces reject files that are not tagged 300 DPI. Very often the pixels are more than sufficient — the only problem is that the tag says 72, because phones and web tools write 72 by default.
This tool fixes exactly that: it rewrites the tag to whatever value you need. Pixels are untouched, the file is never recompressed, and no quality is lost.
But changing the tag does not improve quality
There is a widespread myth that converting a 72 DPI image to 300 DPI improves print quality. It does not. Changing the tag adds no pixels. An 800×600 image tagged 300 DPI is still 800×600 — it now simply asks to be printed at 6.8×5.1 cm.
That is why this tool shows you the print size. It is the number that answers the real question:
- Tagged 300 and the print size covers what you need — your file is ready.
- Tagged 300 but it prints at 5×4 cm — you do not have enough pixels. No tag fixes that; you need a higher-resolution source file.
A rough rule: a full-page A4 print at 300 DPI needs roughly 2480×3508 pixels. Below that, the print will look soft no matter what the tag says.
A JPEG has two separate DPI fields
A JPEG can store its resolution in two places: the JFIF header and the EXIF block. The two can hold different values, and which one takes effect depends on the software opening the file — Photoshop generally reads EXIF.
With tools that write only one of them the story goes like this: you send the file saying you set it to 300, the print shop opens it in Photoshop, sees 72, and it bounces back. This tool writes both, and tells you before converting if your file currently contradicts itself.
PNG keeps this in a separate section called `pHYs`, where there is only one value to worry about. WebP has no such field at all — which is why this tool does not accept WebP, rather than inventing a value it cannot store.
How to change an image to 300 DPI
Step 1: Upload the image
Drop in your JPG or PNG. You can select several files at once.
Step 2: Read what the file declares now
The tool shows the DPI the file currently claims and its pixel dimensions. If there is no DPI at all, it says so.
Step 3: Choose a target
300 is the print standard; 150 is used for newspapers and flyers, 600 for fine-art printing. You can also type any value you need.
Step 4: Check the print size
The physical size at your chosen DPI appears immediately. If it is smaller than you need, the tag is not the problem — the source file is.
Step 5: Download
Save the file. A single image downloads directly, several arrive as a ZIP, and your pixels are preserved exactly.
Frequently Asked Questions
Will converting 72 DPI to 300 DPI make my image sharper?
No. This is the most common misconception about DPI. The tag adds no pixels to the file; it only changes the physical size the file asks for on paper. Sharpness comes from the pixel count, and that does not change.
My printer asked for 300 DPI — is my file good enough?
Look at the print size. The tool shows how many millimetres your image covers at the DPI you chose. If that is equal to or larger than the size you want to print, your file is fine. If it is smaller, you do not have enough pixels, and no tag will fix that.
How many pixels do I need for A4?
At 300 DPI, A4 (210×297 mm) needs about 2480×3508 pixels. At 150 DPI that halves. Below those figures, expect a soft print.
Does this reduce image quality?
No. Only the resolution field in the header is rewritten; the image data is copied byte for byte. Because the file is never recompressed, not a single pixel changes.
Why can’t I upload a WebP file?
The WebP format has no field reserved for DPI, so there is nowhere to write it. If you have a WebP, convert it to JPEG or PNG first, then set the DPI.
Is my file uploaded?
No. Reading and writing both happen entirely in your browser; the file never leaves your device.
Related Tools
- Convert an Image to 300 DPIRe-tag a JPG or PNG as 300 DPI without touching a single pixel — and see, before you send it, whether the file really covers the paper.
- Convert an Image to 600 DPISet a file to 600 DPI without re-encoding it — and find out first whether 600 is what your job actually needs.
- Check the DPI of an ImageFind out what your file really declares — including the case where a JPEG declares two different values at once.
- Photo Metadata & Privacy CleanerSee the GPS location, device details and hidden EXIF/C2PA data in your photo — then strip it in one click.
- Image Compressor & Format ConverterCut file size without visibly hurting quality (WebP / JPG / PNG).
- MP3 Metadata & ID3 Tag RemoverStrip the studio, software and personal details from an audio file, keeping title and artist.