Wasn't happy with the ones generally available as most of them were static and required shifting of cells around. I wasn't even happy with my own excel spreadsheet. This calculator works off jQuery and is dynamic so that you're not shuffling your numbers around trying to remember what class is what.
Maybe it's useful, maybe it isn't. It's derived from one of my many spreadsheets and I'll be working on a trophy calculator as well. It's all about the min/maxing!
http://tranquillityguild.com/rating/