A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
We use Excel Online combined with Microsoft's Excel Services JavaScript API https://msdn.microsoft.com/en-US/library/hh315812.aspx to do similar things (assessment tools/calculators). This can enable you to develop capabilities to: offer a variety of user access scenarios (anonymous to secure login), allow users to save/load data, submit/share assessments, create reports, monitor usage, etc. You might also consider the newer/better JavaScript API for Office (Add-Ins) https://dev.office.com/docs/add-ins/overview/office-add-ins however, it has access limitations that may not work in your scenario. There's also graph.microsoft.com (REST API), but its Excel API is still in beta (also has access and other limitations).
We have various examples on our website: http://analysisplace.com.