I collect some information about the request your browser makes. I will never do anything "evil" with this data - nothing that you wouldn't approve of. I will not show or sell it to other people.
I do not store (or even have access to) any really private information. The site does not have a registration feature and probably won't until it becomes necessary for some functionality.
Percentage Calculator uses server logs for analytics purposes only. IP address, date and time of the request, browser name and version and referrer URL are stored. I'm too lazy to actually analyze these logs, but they're handy when things go south (for example when the server goes down I can look at what was going on before it happened).
If you have questions or comments, the contact form likes to be used.
To sum up, you have nothing to worry about (besides eating too much chocolate, I tend to encourage people to do it).
One line you need to read: Percentage Calculator Android app does not do any kind of funky stuff. It is safe to use it.
Right now the app does not do any kind of logging or tracking. I do intend to show unobtrusive ads to monetize the app and include some 3rd party analytics code to see how you guys use the app so that I can improve it. As with the website, these will be 3rd party services and I don't have much control over what they do, but I'll be sure to use trustworthy partners (I probably will go with Google in both cases, but have not researched the topic yet).