File format metadata
The DPI checker reads resolution metadata directly from the file headers. JPEGs store density in the JFIF header or EXIF resolution tags. PNGs use the pHYs chunk to define pixels per physical unit. WebP files only contain DPI data when EXIF resolution tags are explicitly embedded.
Print size estimation
Pixel dimensions define the actual image data, while DPI is just a metadata tag for print density. The tool divides the raw pixel dimensions by the stored DPI to calculate the physical print size in inches and centimeters. A 2400 × 3000 pixel image with a 300 DPI tag will print cleanly at 8 × 10 inches.
Conflicting resolution tags
A single image can contain multiple resolution values that disagree with each other. This happens when different software writes JFIF and EXIF data at different stages of an edit. The tool surfaces the primary source used and flags any mismatched tags to explain why other applications might report a different DPI.
Unset DPI values
Many files omit physical resolution metadata entirely. Web exports, screenshots, and social media downloads usually have pixel dimensions but no DPI value. A “Not set” result is standard behavior for screen-bound graphics and only becomes an issue for print layouts.