Converting sugar to splenda

I have never converted sugar to splenda I have always just used recipes that call for splenda. So my question is, if a recipe calls for a cup of sugar, do you just use a cup of splenda or do you use less splenda? Is it the same sweetness as sugar or what?

I think this might help, its what I printed out an used: http://splenda.allrecipes.com/default.aspx

Thanks so much