If you can provide the html, css, php, etc. for the webpage on which you would like the calculator made, I will complete the project as soon as I can.
I am a full time computer science student, so the calculator itself and the multiple inputs are not a significant challenge. I would however like to take a few days on this project, as I am currently learning about about different security vulnerabilities in websites (especially those with forms such as this calculator), and want to provide a quality and secure application.
Web design is more or less my summer self-study topic, so I would more than happy to tackle a project like this!