Calculation method of monthly car purchase: 1. Monthly repayment formula of equal principal and interest repayment method: monthly repayment amount = [loan principal × monthly interest rate ×( 1+ monthly interest rate) repayment months ]=[( 1+ monthly interest rate) repayment months-1]. 2. Calculation formula of monthly repayment amount of average capital repayment method: monthly repayment amount = (loan principal ÷ repayment months)+(principal-accumulated amount of repaid principal) × monthly interest rate; 3. After you are optimistic about your favorite model, go to a qualified dealer who cooperates with the bank to buy a car. At the same time, we must sign a car purchase contract. This contract should specify the car price, taxes, insurance payment methods, and also specify the proportion of the remaining mortgage. Everyone should look at them one by one, and don't write a general price.