DPI checker & changer

What DPI actually means

DPI (dots per inch) is a metadata hint that tells print software how large to render the image on paper. It does not change the pixel data. A 3000×2000 pixel image is 3000×2000 pixels regardless of DPI — what changes is the print size:

• At 72 DPI the same image prints at 41.7″ × 27.8″ (a huge poster)
• At 300 DPI the same image prints at 10″ × 6.7″ (a small photo)

That's why "my print shop says my file is too low DPI" is usually a metadata problem, not a resolution problem — the file has enough pixels, the JPEG header just doesn't declare them at the print-ready density.

How this rewriter works

JPEGs store DPI in the JFIF marker (APP0 segment, bytes 11–15). The tool locates that segment in your file, patches the density fields to your target DPI, and writes the file back out. Because we only touch metadata bytes — never the compressed image data itself — there is zero quality loss. The output is byte-identical to the input except for the four density bytes.

Common DPI targets

• 72 DPI — screen / web default (irrelevant for web display; only matters for print)
• 96 DPI — Windows default screen DPI
• 150 DPI — draft print quality; posters viewed from > 1 metre
• 200 DPI — decent print quality; adequate for most flyers
• 300 DPI — standard photo/print quality; the industry default for anything held in hand
• 600 DPI — high-end fine art print and typography-heavy print

Related tools

• Resize image — if you don't have enough pixels for the print size, this is what to use before setting DPI.
• Image metadata viewer — see every EXIF, DPI and camera detail in your file.
• Optimise images for print — full print-preparation guide with per-paper-size dimensions.
• Aspect ratio calculator — compute the print size any given pixel count produces at each DPI target.