Privacy Policy

What happens to the numbers you enter

The BMI calculator does its math entirely inside your browser, using JavaScript. Your height, weight and unit choice are never sent to a server, never logged, and never stored in any database on this site. There is no form anywhere on this site that transmits your height or weight anywhere. This is health-adjacent information, so it is treated with extra care: it simply never leaves your device.

This is a direct consequence of how the site is built: it is a static site with no backend that receives, processes or stores what you type. There is no infrastructure on this site's side capable of receiving those numbers, even if someone wanted to.

Theme preference and last entered values

The only thing this site saves on your device is your light/dark theme preference and your last entered height, weight and unit choice, stored in your browser's localStorage. This does not identify you, is never sent to any server, and only exists so the calculator can remember your inputs on your next visit to save you re-typing them. You can clear it at any time by clearing this site's data in your browser.

The feedback button

Below the calculator there is an optional thumbs-up / thumbs-down feedback button. Clicking it sends an anonymous signal (just the vote count, no information that identifies you, no stored IP address, no tracking cookie, and definitely not your height or weight) to this site's backend, purely so the count can be tallied. A local marker in your browser prevents you from being asked to vote again repeatedly, but that marker does not identify you personally.

Anonymous engagement measurement

This site measures a small set of anonymous, aggregate engagement signals so the tool itself can be improved: how quickly a visitor starts interacting with the page after it loads, whether the calculator was actually used (a result was produced), whether a visitor left again within 10 seconds without interacting at all, and roughly how long a visitor stayed on the page (bucketed into ranges, not an exact duration). It also records a coarse category for where a visit came from (Google, Bing, a direct link, or "other"), never the full referring URL or any search terms.

None of this identifies you: there is no cookie, no session identifier, no stored IP address, and no browser fingerprinting anywhere in this measurement. Each page view is treated as a standalone, anonymous event sent once when you leave the page, using your browser's built-in sendBeacon mechanism to this site's own backend (not a third-party tracker). It cannot be linked back to a specific visitor, a specific device, or your calculator inputs.

Cookies

This site does not use advertising tracking cookies or third-party profiling cookies. The only local storage used is the localStorage mentioned above, for theme preference and calculator values, which is technically not a cookie and is not automatically sent to any server with every request, unlike a traditional cookie.

Hosting and infrastructure

This site is hosted on Cloudflare's network, which processes the technical requests needed to deliver the page to your browser (source IP address, browser type, request time), the same way any hosting provider does. That technical infrastructure data falls under Cloudflare's own privacy policy as the network operator, and is not accessed, exported or combined by this site to identify visitors individually.

This is not medical advice

This site provides a calculation tool and general reference information, not medical advice, and does not collect health information about you beyond the numbers you optionally type into the calculator on your own device (and which never leave it, per above). For questions about your own health, weight, or BMI result, consult a doctor or another qualified healthcare provider.

What this site does not do

To be explicit rather than vague: there is no user account system, no login, no email newsletter signup, no advertising network, no remarketing pixel, and no sale or sharing of visitor data with data brokers. The only measurement on this site is the anonymous, aggregate engagement signal described above: nothing here identifies you personally, and no personal information is requested, required, or collected.

Changes to this policy

If the way this site collects or handles data changes in the future (for example, if a new feature required saving something on a server), this page will be updated to reflect that change before it takes effect. There is no fixed review schedule, but the commitment is to keep this text matching what the tool actually does, not a generic description copied from elsewhere.