I'm a solo indie dev from China, and I got tired of BMI calculators that force you to sign up, drown you in ads, ignore imperial units, and just hand you a cold number with no context.
So I built my own. It's completely free, no signup, no ads, and 100% client-side — everything runs locally in your browser, and no data ever leaves your device.
It supports metric and imperial switching without reloading, live BMI updates, and proper input validation. The part I'm most happy with is a horizontal gradient band from blue to green to yellow to red, with a dynamic marker showing exactly where your BMI sits. You don't just see "24.1" — you see your position in the range.
It's all vanilla HTML, CSS, and JavaScript. No frameworks, no backend, no tracking. I'm building this in public and would love honest feedback — especially from webdev folks who care about privacy-first frontend tools.
If it's useful, I've also built 20+ other no-signup, pure frontend tools on the same site.
Try the BMI Pro tool here: https://app.lihayo.com/bmi-pro/
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