A tiny print DPI & size calculator (no upload, no dependencies)

When you prepare artwork for print or POD, you eventually need the boring math: how large will 5400×7200 px print at 300 DPI? or how many pixels do I need for an 18×24 inch poster? I kept reaching for a search engine to answer the same conversion, so I made a single-page calculator that runs entirely in the browser.

What it does

• Pixels → print size: enter width/height in pixels and a DPI (PPI) value; get inches, millimetres, aspect ratio, and megapixels.
• Print size → pixels needed: enter a target size (in/mm/cm) and DPI; get the required pixel dimensions.
• Common presets (18×24 @300, 12×12 @300, 15×18 @300, 8×10 @300) because those are the sizes I keep reusing.

There is no upload, no account, and no network call — it’s plain HTML/JS doing the arithmetic in your browser. It won’t inspect your files or tell you whether a specific print service will accept them; for that you still need to check the service’s current spec. 300 DPI is a common rule of thumb for close viewing, but large-format prints viewed from a distance can work at lower DPI.

Try it

• Calculator: https://aefristore.web.app/tools/print-dpi-calculator.html
• Storefront: https://aefristore.web.app

AI disclosure

I used AI assistance (an AI coding agent) to write this post and to help build the calculator. The tool’s behaviour is simple arithmetic (pixels ÷ DPI = inches) and you can verify the results with any calculator.