I made a little GWT App for personal use a couple of months ago. Posting it in case other people find it useful. If you don't trust Javascript: sources can be downloaded here and you can run it inside a cocoon or something.

How to use
fill in a delay and press "Calculate" other optional fields let you enter a specific amount of sTP during WS and number of WS hits that connect including offhand hit in case of Dual Wield. There's a list of popular sTP gear on there as a reference.

I'll probably take it down after a while. If you think it's useful (cus, like me, you can't do base TP and sTP calculations in your head) you should probably download it and keep a copy locally jic.