Here are two calculators I use that don't require that you download anything to your computer.

I've use the one at handloads.com a lot. The results have always been very close to my real world experience. The only downside is there is no provision for printing the results. But you can do a screen capture or "snip" to save it to you PC as a picture file and print that.

http://www.handloads.com/calc/

This one is for round balls. I haven't used it much, nor have I attempted to verify the results.

http://www.ctmuzzleloaders.com/ctml_...allistics.html