conversation: User (FirstTimeWang): "I'm overpaying my monthly installment by 1/12 of a payment, equalling an extra payment per year. I confirmed with the bank today that the excess payment is going towards the mortgage principal and NOT interest.\n\nIs there a calculator where I can dump my values and see how much money I'm saving. I'll also accept a formula and do it the old fashioned way if I have to.\n\nThanks!\n\nEdit: you are all doing God's work. You are all made of star stuff."
  Self: "Someone developed and posted this a few days ago: http://paydowncalc.com/\n\nI found the monthly, annual, and one time extra payment options really unique and helpful.  "
  