Web-based/online Usable Space Calculator, based on TR-3838.
I occassionally use the awesome Windows tool here, but didn't want to have to fire up a Windows VM to use it or break out my spreadsheets, so I created this. These two are not related and this is not a NetApp funded/official tool. It is my own personal project I thought I'd share so others may be get some use out of it.
It is hosted on GitHub and GitHub Pages. You can view the source code for the calculations and known issues. When you first load the page, some inputs are there by default. Just change what you need and the calculations will update automatically.