I have not seen the calculator on this site. The one I use only gives me the P&I payment. I prefer that because I am looking at properties both inside and outside the city limit along with short sales. The calculators can't take into consideration the tax variables. I find it easiest to use the calcs for P&I and then look the properties tax value up on the county govts website. This way I have the most accurate payment. Insurance I just estimate based on my experience. You could always call your local agent to get an estimate on how insurance runs in your area.
This one is spot on.....If you know the loan amount, the taxes and the estimated annual insurance it will be spot on.
It matches my actual mortgage exactly once I add the monthly PMI amount to the payment.