This Calculator is a handy way to estimate your monthly payment, however, it does not factor in the exact TAXES which can really change the monthly amount. If you have a specific home you are trying to determine the monthly payment on, simply Look at the total property & school tax and divide by 12. The lender will want to escrow this amount so that when the next bill is sent out they have the funds to pay it.
In addition, if there are HOA fees ( Homeowner Association) as in many of our Pocono communities you should also factor that in as a monthly cost so they are in your budget. Finally, the best way to determine an estimate is to work with a lender who will be happy to do estimates for you.