Interest is the amount of money the financial institutions charge on top of the principal amount. It is calculated based on the home loan interest rate and the principal amount. The interest is added to the principal amount to make the monthly EMI.  You can calculate the total interest applied on the principal amount in just 3 easy steps by using PNB housing home loan EMI calculator. Step 1 - Enter the principal amount. Step 2 - Select the ROI. Step 3 - Enter the tenure of the home loan you want to lend to.