Student loan payments are calculated based on the details of your loan. When you take out a private student loan, the lender will base your monthly payment amount on your repayment period, the total amount you borrowed, and your credit score. With federal student loans, your monthly payment amount will be calculated based on the amount you borrowed and the interest rate through the default standard repayment plan, which is 10 years. Typically, the higher your interest rate and loan amount, the higher your monthly payment will be. And typically, the longer the loan repayment term, the lower your monthly payment will be.