Mortgage Calculator using the U.S. Formula This calculator calculates U.S. monthly mortgage payments based on principal, interest and term. U.S. mortgages are compounded monthly. Amortization(Years) = Term (Years) = Yearly Interest Rate (%) = Principal Amount ($) = Downpayment (%) = Downpayment Required ($) = Mortgage Principal ($) = Monthly Payment ($) = Still Owing at End of Term ($) =