Where to go from here
This page answers one question: what the payment is. Two others usually follow. If you are wondering what happens when you throw extra money at the balance, the prepayment calculator shows how much interest an extra $200 a month actually saves and how many years it cuts off. If you have not committed to buying yet, the rent vs buy calculator works out whether the tax benefit everyone assumes you get is worth anything in your bracket — for a lot of buyers it is exactly zero.
What this page assumes
Figures are estimates for planning, not a loan offer. Specifically: the rate is fixed for the whole term, so ARMs are not modeled; property tax and insurance are held flat for the life of the loan when in reality both rise, and the property tax rate is a statewide median that varies enormously by county and neighborhood; PMI is estimated at 0.60% of the loan per year and is assumed to end automatically at 80% loan-to-value, though lenders differ and some loan types carry it for the full term; closing costs, points, and any escrow shortfall are not included; and the payoff date assumes every payment arrives on time and none of them are early. Confirm anything consequential with your lender.