Privacy Policy

Last updated: September 2026

The calculator itself

Contact Lens Calculator is free to use and does not require an account. The prescription values you enter into the calculator are converted in your browser. They are not sent to a server unless you choose to use the "Email My Results" feature described below.

Email My Results

If you enter your email address to have your converted prescription sent to you, that email address and the prescription values you entered are stored in a database so the results can be delivered. This is optional: the calculator works fully without it, and nothing is stored unless you submit the form.

Analytics

This site uses Google Analytics 4 to understand how many people visit and which pages are useful, using a measurement ID set at build time. Google Analytics uses cookies and similar technologies and may collect information such as your approximate location, device and browser type, and the pages you visit. See Google's privacy policy for how Google handles this data.

Local storage

The site may store a light/dark theme preference in your browser's local storage so the site remembers your choice on your next visit. This stays on your device and is not sent to us.

Affiliate links

Some links to contact lens retailers on this site are affiliate links: if you click one and make a purchase, the retailer may pay a commission. This does not change the price you pay. See the affiliate disclosure page for details.

Changes to this policy

If how this site handles data changes, this page will be updated and the date above will change.