EQTraders have a calculation engine, as they are specialists, i think it's pretty accurate. Perhaps someone with lotsa charism could ask them if they could share their calculation formulas...
http://eqtraders.com/calculators/mai...r=130000000000
For Eqtraders, you always have 5% chances of success, whatever your skill and the trivial level are. You can't excess 95% chance of success.