In this paper several types of loans offered by banks and other micro financial institutions are shown, and their respective effective interest rates are calculated. The parameters that affect the effective interest rate, which is the only real parameter that show whether a loan is affordable or not are considered. Some examples of loans without a fee, and those with fees are given and the effective interest rate for those loans is calculated. The mathematical technique for calculation of the effective interest rate is shown, and the financial consultant CASIO FC 100V is used to mathematically calculate the effective interest rate.