How HealthTools works
HealthTools is a free, private health calculators hub. Every calculation runs entirely in your browser — there is no backend, no upload, and no signup. Your health numbers never leave your device — all math runs in your browser..
Your health figures are never uploaded
There is no server. Each calculator is a small pure function that runs as JavaScript in your tab. The Content-Security-Policy (connect-src 'self') restricts which hosts the page may contact, so the privacy guarantee is enforced by the browser itself. The Cantonese food calorie database is a build-time static snapshot bundled same-origin — it makes no runtime request to any server.
Real, hand-verified math
Each calculator implements a standard published method — the WHO BMI bands (Asian-Pacific and Western), the Mifflin-St Jeor BMR equation, the US Navy body-fat method, Naegele's rule for the due date. A verify suite (npm run verify) hand-checks reference values (for example BMI 70 kg / 175 cm = 22.9; BMR 80 kg / 180 cm / 30 y male = 1,780 kcal) before every build, so the math is real and reproducible, not a placeholder.
No WASM, no CDN, no tracking
HealthTools is pure JavaScript math plus inline SVG. It needs no WASM, no Canvas, no Web Crypto, and no cross-origin isolation — so the CSP is one of the simplest in the portfolio (script-src 'self' with no 'wasm-unsafe-eval', no COOP/COEP). Every asset is bundled same-origin.
A note on accuracy
These tools are educational estimates, not medical advice. Body-fat and calorie methods carry real-world error, and individual variation is large. Educational estimate only — not medical advice. See a qualified professional for decisions about your health.