How do I change an image to 300 DPI?

Upload it, set 300, leave the method on “Keep pixels” and download. Four header bytes change and the image data is copied across untouched.

Will changing the DPI make my image better quality?

No. It changes how large the image prints, not how much detail it holds. A low-resolution photo at 300 DPI simply prints smaller.

Why does my image say 72 DPI?

Either the file states 72, or it states nothing and software assumes 72 by convention. Both are common in images that came from the web or from a screenshot.

What DPI do I need for printing?

300 is the standard for photographic printing and most submissions. 600 is used for line art and text scans. Large-format prints viewed from a distance are often produced at 150 or less.

Does this work for PNG?

Yes. PNG stores density in a pHYs chunk in pixels per metre; the chunk is written or replaced and the image data is untouched.

Image DPI Converter

Change an image's DPI to 300, 600 or anything else by rewriting one header field — without resampling, recompressing or touching a single pixel.

Runs in your browser — nothing is uploaded

Your image

Choose an image

New DPI

Your file never leaves this device. The whole operation runs in your browser — nothing is uploaded, queued on a server, or deleted later, because nothing was ever sent.

Print size at this DPI

—

Choose an image to begin

Changing DPI does not change the image

DPI is an instruction to a printer, not a property of the pixels. A 3000-pixel-wide photo is 3000 pixels wide at 72 DPI and at 300 DPI — all that changes is how large it prints. On “Keep pixels” this tool rewrites one header field and copies the image data across untouched, so nothing is recompressed.

Why use it

Built to be genuinely useful

The pixels are not touched

DPI is a header field. Changing it rewrites four bytes and copies the image data across untouched.

Print size, before and after

See exactly how large the file will print at 72, at 300, and at whatever you choose.

Resampling is optional and labelled

Available when a printer genuinely asks for it, off by default, and honest that it is lossy.

JPEG and PNG

JFIF density for JPEG, the pHYs chunk for PNG — both written properly.

How it works

Three steps

1
Choose your image. The DPI it currently declares is shown, if it declares one.
2
Pick a new DPI — 300 for print, 72 for screen, or type your own.
3
Download. On “Keep pixels” the image data is identical to what you uploaded.

DPI does not change the image

This is the single most common misunderstanding in image work, and most so-called DPI converters make it worse. DPI is not a property of the pixels. It is a number stored in the file's header that tells a printer how densely to lay those pixels down, and nothing else in the world reads it.

A 3000-pixel-wide photograph contains exactly 3000 pixels of detail whether the header says 72 or 300. At 300 DPI it prints ten inches wide; at 72 it prints nearly forty-two, and looks soft because the same detail is spread further. The file is byte-for-byte identical apart from those four header bytes.

So when a print shop or a submission portal asks for 300 DPI, they are almost always asking for a header value. That is a metadata edit, and it should be instant and lossless. A tool that resamples your photo to satisfy it has degraded the image to change a label.

When resampling is actually what you want

There is a real operation behind the confusion. If you need an image to print at a specific physical size at a specific density — say exactly four inches wide at 300 DPI — then it must contain 1200 pixels across, and changing the pixel count means resampling.

Scaling down is fine and often improves apparent sharpness. Scaling up is not: no algorithm can recover detail the sensor never captured, and enlarging a 600-pixel image to 1200 produces a larger, softer version of the same picture rather than a more detailed one. Anything promising otherwise is guessing at plausible pixels.

That is why resampling here is a separate, clearly labelled mode. If someone has asked you for “300 DPI”, try the metadata edit first — it satisfies almost every such request.

Working out the numbers yourself

Print size in inches is pixels divided by DPI. A 2480 by 3508 image at 300 DPI prints at 8.27 by 11.69 inches, which is A4 — and that is exactly why scanners default to those dimensions.

Going the other way, to fill A4 at 300 DPI you need 2480 by 3508 pixels, and at 600 DPI you need twice that in each direction, which is four times the pixels. This is where scan sizes come from and why a 600 DPI scan of a document is so much larger than a 300 one.

For anything shown on a screen, DPI is irrelevant. Browsers, phones and televisions read pixel dimensions and ignore the header entirely, which is why a web image's stated DPI never matters.

FAQ

Questions people ask

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