Change Image DPI to 300, or Any Other Value

Rewrite the DPI value saved inside a JPEG or PNG. The pixels and the quality stay exactly as they are, and you see the file's current DPI and its new print size.

Runs in your browserFree, no sign-upLast reviewed October 13, 2026

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Quick answers

How do I change an image to 300 DPI?: Choose the JPEG or PNG above, leave New DPI at 300 and download the result. The DPI value in the file header is rewritten and the pixels are left untouched, so there is no quality loss.
Does changing DPI to 300 improve image quality?: No. DPI is only an instruction about print size. The image has exactly the same pixels before and after, so it is no sharper. To print larger at a true 300 DPI you need an image with more pixels.
What does changing 72 DPI to 300 DPI actually do?: It makes the image print smaller and denser. A 3000 x 2000 pixel photo marked 72 DPI is laid out at 41.67 x 27.78 inches. Marked 300 DPI, the same pixels are laid out at 10 x 6.67 inches.
How do I check the DPI of an image?: Choose the file and read Previous DPI in the result. It shows the resolution stored in the file and which header field it came from, or Not set if the file has none. Pixel dimensions are shown beside it.
Does changing the DPI change the file size or pixel dimensions?: Pixel dimensions never change. File size stays the same when the file already has a resolution field. If it has none, a small header is added: 18 bytes for a JPEG, 21 bytes for a PNG.
Why do I need 300 DPI?: Printers, publishers and some upload forms ask for it because 300 pixels per inch is the usual standard for sharp prints viewed up close. Many automated checks read only the DPI value in the file, which is what this tool sets.

What Image DPI Converter does

DPI is a number stored in an image file's header that tells print and layout software how large to make the picture. This tool changes that number, to 300 by default, and nothing else. In a JPEG it writes the JFIF density and, where present, the EXIF resolution tags and the Photoshop resolution record. In a PNG it writes the pHYs chunk. The image data is copied through byte for byte, so the file is not re-compressed or resized. That also means no detail is added: a 600 x 400 pixel image set to 300 DPI is still 600 x 400 pixels, and now prints at 2 x 1.33 inches. The file is processed in your browser and is not uploaded.

Print size at 72 DPI and at 300 DPI for common image sizes

The pixel dimensions are fixed. Changing the DPI only changes the size a printer or layout program assumes. These are the Print size values the tool reports.

Pixel dimensions	Print size at 72 DPI	Print size at 300 DPI
413 x 531	5.74 x 7.38 in	1.38 x 1.77 in (3.5 x 4.5 cm)
600 x 600	8.33 x 8.33 in	2 x 2 in (5.08 x 5.08 cm)
1200 x 1800	16.67 x 25 in	4 x 6 in (10.16 x 15.24 cm)
1500 x 2100	20.83 x 29.17 in	5 x 7 in (12.7 x 17.78 cm)
1920 x 1080	26.67 x 15 in	6.4 x 3.6 in (16.26 x 9.14 cm)
2400 x 3000	33.33 x 41.67 in	8 x 10 in (20.32 x 25.4 cm)
3000 x 2000	41.67 x 27.78 in	10 x 6.67 in (25.4 x 16.93 cm)
4032 x 3024	56 x 42 in	13.44 x 10.08 in (34.14 x 25.6 cm)
6000 x 4000	83.33 x 55.56 in	20 x 13.33 in (50.8 x 33.87 cm)

To find the pixels needed for a given print size, multiply each side in inches by the DPI. An 8 x 10 inch print at 300 DPI needs 2400 x 3000 pixels.

DPI, pixels and print size formula

print size in inches = pixels / DPI

The three values are tied together, and a file only stores two of them: the pixels and the DPI. Print size is worked out from those. Raising the DPI without adding pixels therefore shrinks the print size by the same factor. Going from 72 to 300 DPI makes the print 4.17 times smaller on each side. To keep the print size and raise the DPI, the image must be resampled to more pixels, which is resizing, not a DPI change.

Why changing DPI does not add detail

An image is a grid of pixels. DPI is a label attached to that grid that says how many of those pixels to place along each inch of paper. Changing the label does not create pixels, so it cannot make a blurry photo sharp or a small image suitable for a poster.

On a screen the label is ignored altogether. Web browsers, phones and most viewers show an image according to its pixel dimensions, so a 72 DPI file and a 300 DPI file with the same pixels look identical on screen.

What the label does affect is print and layout. Word processors, page layout software and photo kiosks use it to decide the starting size of a placed image, and submission systems often check it. Setting 300 DPI satisfies those checks honestly only when the pixel count is high enough for the size you are printing. If it is not, resize the image to the print size you need with Resize Image in Inches, which changes the pixels and sets the DPI together, and expect an enlarged image to look softer.

What the tool writes to the file

Different programs read resolution from different places, so every one that exists in the file is updated to the same value.

JPEG, JFIF header: the density unit is set to dots per inch and the horizontal and vertical density to your value. If the file has no JFIF header, as with many camera files, an 18-byte one is added at the start.
JPEG, EXIF: if the EXIF block has XResolution and YResolution tags they are overwritten in place, and ResolutionUnit is set to inches. No other EXIF value is touched.
JPEG, Photoshop data: if the file carries a Photoshop resolution record, it is updated too, so software that reads it does not show the old figure.
PNG, pHYs chunk: replaced, or inserted after the header chunk if missing, with a correct checksum. An eXIf chunk with resolution tags is updated as well.
Everything else, including all compressed image data, colour profiles and other metadata, is copied unchanged.

How DPI is stored in a PNG: pixels per metre

PNG has no DPI field. It records whole pixels per metre, so most DPI values cannot be stored exactly. The tool shows the stored figure, and software rounds it back when displaying it.

DPI entered	Pixels per metre stored	Exact DPI that represents
72	2,835	72.009
96	3,780	96.012
150	5,906	150.0124
200	7,874	199.9996
240	9,449	240.0046
300	11,811	299.9994
350	13,780	350.012
600	23,622	599.9988
1200	47,244	1199.9976

The conversion is DPI / 0.0254, rounded to the nearest whole number. JPEG stores DPI as a whole number directly, so 300 is stored as exactly 300.

Worked examples from real files

JPEG from 72 to 300 DPI

A 600 x 400 pixel JPEG marked 72 DPI, New DPI 300

Previous DPI 72, read from the JFIF header. Print size at 300 DPI: 2 x 1.33 in (5.08 x 3.39 cm). File size the same as the original

Only four header bytes differ between the two files.

PNG with no resolution set

A 600 x 400 pixel PNG with no pHYs chunk, New DPI 300

Previous DPI Not set. A pHYs chunk of 11,811 pixels per metre is added, making the file 21 bytes larger. Print size 2 x 1.33 in

JPEG that also has EXIF resolution tags

A JPEG with a JFIF header and EXIF tags both saying 72 DPI, New DPI 300

Both are set to 300 and the file size does not change. The decoded pixels are identical before and after

Using Image DPI Converter

1
Choose your file under Image (JPEG or PNG). Files up to 30 MB are accepted.
2
Enter the value you need in New DPI. It defaults to 300 and accepts whole numbers from 1 to 65,535.
3
Read Previous DPI to see what the file was set to, and Print size to see how large it will print at the new value.
4
Download the result. The file name ends with the new DPI.

Common questions

Is the image re-compressed when I change the DPI?

No. The compressed image data is copied byte for byte and only the resolution fields in the header are rewritten. A JPEG can be run through this tool any number of times with no generation loss.

Is my image uploaded to a server?

No. The file is read, edited and saved by your browser on your own device. The image is not sent anywhere.

How do I increase the DPI of an image without losing quality?

Changing the DPI value, as this tool does, never loses quality because the pixels are not touched. What it cannot do is increase real resolution. For more detail at the same print size you need a higher-resolution original.

Why does my PNG show 299.9994 DPI instead of 300?

PNG stores resolution as whole pixels per metre. 300 DPI is 11,811.02 pixels per metre, which has to be saved as 11,811, and that works out to 299.9994 DPI. Image editors and print software display it as 300.

Which image formats can I change the DPI of?

JPEG and PNG. Other formats, including WebP, GIF and HEIC, are rejected with a message. Convert the image to JPEG or PNG first with the Image Format Converter.

Can I enter a decimal DPI such as 72.5?

No. The JPEG header stores DPI as a whole number, so the tool accepts whole numbers from 1 to 65,535 for both formats.

My image has no DPI at all. What does that mean?

Some files carry no resolution information, and software then assumes a default, commonly 72 or 96. The tool shows Previous DPI as Not set in that case and adds the field with your value.

What DPI should I choose for print, screen and scans?

300 is the usual request for photos and documents printed at normal viewing distance. 150 is often enough for large posters viewed from further away. 600 is used for line art and fine text. For screens the value has no effect.

How do I know whether my image has enough pixels for 300 DPI?

Divide the pixel dimensions by 300 to get the largest print size in inches, or read Print size in the result. The Print Size and DPI Calculator on this site does the same sum without needing a file.