Privacy Policy.

Last updated: 2026-06-06

Summary

Your inputs — age, gender, height, weight, waist and activity — stay in your browser. We do not collect, store, or transmit them to any server. To understand how the site is used, we load Google Analytics on every page (aggregate traffic only, IP anonymised). We also load Google AdSense for advertising; whether the ads shown are personalised or contextual is controlled by your choice on the cookie banner.

What the calculator does with your data

The BMI calculator on this site runs entirely in JavaScript on your device. When you type your age, gender, height, weight or waist, the calculation happens locally and the result is rendered into the page. The only persistence is localStorage on your own device, used for:

• Saving your last form state so you do not have to re-type on return visits.
• Saving up to 20 "Save to history" entries you explicitly saved.
• Saving your cookie-consent choice.
• Saving your theme preference (light / dark / auto).

None of this is sent to a server. You can clear it at any time by clearing site data in your browser.

What we measure (Google Analytics)

We use Google Analytics 4 (gtag.js) on every page to understand aggregate traffic patterns. The data sent on each page view is:

• The page URL you visited.
• The referring page (if you arrived from another site or search engine).
• Your country and city (derived from your IP; the last octet is discarded before storage because we send anonymize_ip: true).
• Your browser, operating system, screen size, and language.
• An anonymous, randomly-generated Client ID and Session ID (used only to count unique visitors and sessions).

We do not send form values, page-search terms, health data, or any custom events that identify you personally. Google signals, advertising features, and remarketing are turned off in the GA4 property, so Analytics data is not used to personalise the ads you see.

You can block Google Analytics entirely with the Google Analytics Opt-out Browser Add-on, or by using a content blocker / privacy-respecting browser that filters googletagmanager.com.

Cookies we use

• Consent preference — stores whether you chose Accept (personalised ads) or Decline (non-personalised ads) on the cookie banner (fbcoConsent:v1 in localStorage). The site itself does not read this value for any purpose other than to pass it to the ad network.
• Google Analytics — sets _ga and _ga_* cookies (typically 13 months) to distinguish unique visitors and sessions. We do not use Google Analytics Advertising Features, so these cookies are not used for ad personalisation or cross-site tracking by this site.
• Google AdSense — the site's ad network. AdSense loads on every page; the difference between Accept and Decline on the cookie banner is whether the ads shown are personalised (selected using AdSense cookies that record your visit to this and other AdSense partner sites) or non-personalised (contextual, with no cross-site tracking). AdSense also uses cookies for frequency capping and basic ad measurement.

Third-party services used on this site

The following third-party services are loaded on every page:

• Google Analytics 4 — aggregate traffic measurement (privacy policy, how Google uses data from partner sites). See the What we measure section above for what is collected.
• Google AdSense — display advertising (privacy policy, how ads are personalised). AdSense may read or set cookies in your browser for the purposes described above.

The site does not use Meta Pixel, Hotjar, Microsoft Clarity, Mixpanel, Segment, or any other analytics or retargeting service.

Children's privacy

The site is a general-audience health tool. We do not knowingly collect personal information from children under 13. The calculator can be used in Child / Teen mode for ages 2–19, but the data is processed in the browser and never leaves the device.

Your rights (GDPR / CCPA)

We do not hold personal data on our servers. Google Analytics and Google AdSense each collect their own data under their own privacy policies; to exercise your rights (access, correction, deletion, portability, objection) against that data, contact Google directly through your Google account or via the Google privacy policy. You can change your ad-personalisation choice at any time by clearing site data in your browser, which will cause the cookie banner to reappear on your next visit.

Data breaches

We do not hold personal data on our servers, so a data breach on our side would not expose user form inputs. If a third-party service is breached, we will follow the breach-notification requirements of GDPR / CCPA / applicable law.

Changes to this policy

We may update this policy as the site evolves. The "Last updated" date at the top of the page reflects the most recent change. Material changes will be highlighted on the home page.

Contact

For privacy questions, see our Contact page.