For many teenagers, it’s difficult to understand the true burden of student loans. For someone whose primary source of income has been mowing lawns, the average college graduate starting salary of over $51,000 often seems a little bit like winning the lottery. Unfortunately, it also leaves many feeling like student debt will be no problem. Variations on the theme of, if I’m making $50,000 a year, it won’t take any time to pay off $50,000 in student loans, abound. However, the facts are somewhat different: all-in, college ends up costing more than most families anticipate, and most of that difference gets made up by borrowing. So a student who starts school planning to borrow $25,000 may likely end up owing $30,000 or more. In fact, the average student loan debt for the class of 2017 was over $39,000. But again, it is not unusual for a teenager to see those numbers and do the mental math of, “$51,000 salary – $39,000 loan debt = $12,000 leftover = $1,000 per month which is about $900 more than I have right now.”

A better tool than mental math is a loan repayment estimator such as this one on the Federal Student Aid website. Students can plug in four years’ worth of loans and get estimated monthly payments, or use average balance by institution type (4-year public, 4-year private). The calculator shows monthly payments under various repayment options. One thing to remember: if you choose “average loan balance” it will also show you the current average interest rate. With interest rates rising, the rates shown are lower than what current students will pay. For example, this year’s Direct Student Loan interest rate is 5.05%, whereas the calculator uses an interest rate of 3.9%. You’ll need to add at least $15 per month to the payment to account for future interest rate increases– more for a student receiving unsubsidized loans who will not be making payments during their years in college.