Site analytics lets us see how many users we get to the site, and also some information such as screen resolution and browser information that helps us make the site look good across different platforms. It is not possible for us to idenitfy any individual user from this data, only identify overall patterns of site usage.
If you do not wish your use of this (any many other) sites to be recorded, please conside installing the Google Analytics Opt-Out Browser Add-On.
The advert that is displayed on this site is provided by Google Adsense, just like many many other ads you see on various sites across the web. Cookies may allow Adsense to identify your browser across different sites to present adverts that Google thinks are relevant to your interests. We do not get to see this information.
Away from this nonsense, back to the calculator!