What does Image DPI Converter do?
Convert a JPG or PNG image to 72, 96, 150, 300, 600 or custom DPI in your browser. DPI describes intended print density; pixel width and height determine the detail already in the file. Change DPI metadata alone to keep the same pixels and change the calculated print size, or resample pixels to keep the original physical print size. Neither mode invents photographic detail. Use the inches/centimeters calculator to check the result before downloading.
How to use Image DPI Converter
- 1Choose a JPG, PNG or WebP image and review pixel dimensions and detectable DPI.
- 2Confirm the current DPI, then select 72, 96, 150, 300, 600 or a custom target.
- 3Choose metadata-only mode or resample pixels to preserve physical print size.
- 4Review pixels, print size, and whether the image covers common print sizes, then export.
Supported inputs and outputs
Inputs
JPEG/JPG, PNG, WebP for inspection only
Outputs
JPEG with JFIF DPI metadata, PNG with pHYs resolution metadata
Practical uses
- Setting 300 DPI for print workflows
- Correcting missing print-density metadata
- Calculating inches or centimeters
- Resampling for a fixed physical print size
Browser and media limitations
- Changing metadata alone does not add pixels or image detail.
- WebP export is disabled because this pipeline cannot reliably write standard WebP DPI metadata.
- Resample mode re-encodes image pixels.
- Very high DPI resampling can exceed Canvas and browser memory limits.
- A print application may apply its own scaling rules.
How local processing works
Image bytes are inspected and processed with lightweight browser APIs in this tab. These tools do not load FFmpeg and do not upload the image or metadata.
DPI, pixels and print size are different measurements
A 3000 × 2000 pixel image contains the same pixel detail whether its metadata says 72 DPI or 300 DPI. At 300 DPI, its nominal print size is 10 × 6.67 inches; at 72 DPI, it is about 41.67 × 27.78 inches. Changing only the DPI field changes that print-size calculation, not the underlying image samples.
Choose metadata-only when a printer or publishing workflow needs a resolution value but you do not want to alter the pixels. Choose resampling only when you need different pixel dimensions for a fixed physical print size. Upsampling creates more pixels by interpolation, not new camera detail; downsampling can discard detail.
Why an ordinary browser export can reset resolution metadata
Canvas exports normally write 96 DPI where the output format supports resolution metadata. This tool explicitly patches JPEG resolution fields or PNG pHYs data and verifies the result, rather than trusting that default. WebP resolution writing is disabled because this pipeline does not implement it reliably.
For a 10 cm print at 300 DPI, the required width is 10 divided by 2.54 times 300, or about 1181 pixels. If the source is only 600 pixels wide, changing its DPI label does not create that detail. Ask the print provider whether it needs a metadata value, a minimum pixel size, or both.
What convert to 300 DPI actually changes
In metadata-only mode, a 3000 x 2000 image stays 3000 x 2000 pixels. At 300 pixels per inch its intended print size is 10 x 6.67 inches, or about 25.4 x 16.93 centimeters. That pixel count covers a 4 x 6 inch print at 300 DPI, which needs 1200 x 1800 pixels. It does not cover 8 x 10 inches at 300 DPI, which needs 2400 x 3000 pixels. Choosing resample instead changes the pixel count to hold physical size approximately constant. If that would exceed the browser safety limit, the tool asks you to change settings rather than silently producing the wrong print size.
Frequently asked questions
How do I change an image to 300 DPI?
Upload a JPG or PNG, confirm its current DPI if known, select 300 DPI, then choose metadata-only or resample mode. Review the pixel and print dimensions before export.
Does converting 72 DPI to 300 DPI improve quality?
No. Metadata-only conversion keeps the same pixels; it changes intended print density, not detail.
What does preserve physical print size mean?
Pixel dimensions are multiplied by new DPI divided by old DPI, keeping width and height in inches unchanged.
Which formats get real DPI metadata?
JPEG uses JFIF density fields and PNG uses a pHYs chunk. WebP writing is disabled.
Can I calculate centimeters?
Yes. Switch the print calculator between inches and centimeters.
Is metadata-only JPEG conversion lossless?
The compressed image data is retained; only the JFIF density segment is added or updated.