Body fat from one photo — analyzed once, then deleted. Here's how I built it.

I kept wanting a number between "guess in the mirror" and "book a $150 DEXA scan." Calipers need a second person and a steady hand. Smart scales swing a few points depending on how much water you drank. So I built realbodyfat.com: upload one full-body photo, get body fat %, lean mass and fat mass in about ten seconds.

The constraint that shaped the whole thing: the photo is analyzed once and discarded. No account, so there's no row to attach it to. Nothing is written to disk, and nothing is used for training. That turned out to drive most of the architecture.

The stack

Astro on Cloudflare Workers. The marketing pages, the free US Navy tape calculator, and ~190 programmatic pages (body-fat-by-waist, Army max-waist by height, method comparisons) are static and served from the edge. The photo scan is the only dynamic part.

A single React island for the scan flow — image picker, the request, the result card. The rest of the site ships zero JS.