How the standard payment is worked out
Student loans on a fixed schedule are amortized: the payment stays level, and each month interest is charged on whatever balance is left. Early payments are mostly interest; later ones are mostly principal. The default 10-year term above matches the standard repayment schedule most federal borrowers are placed on unless they choose otherwise.
Why a weighted average rate is the right input
Most borrowers hold several loans taken out in different years, each at its own rate. Entering the weighted average โ each loanโs rate multiplied by its share of your total balance โ gives a far more accurate payment than picking one loanโs rate. Your servicerโs dashboard lists the balance and rate of every loan you hold.
Extra payments and the capitalization trap
Every dollar above the scheduled payment goes to principal, so future interest is charged on a smaller balance โ which is why a modest extra amount compounds into years off the term. Two practical cautions: tell your servicer in writing to apply extra money to the principal of your highest-rate loan, otherwise it may simply advance your due date; and remember that unpaid interest can be capitalized (added to principal) after periods of deferment, forbearance or some plan changes, permanently raising the balance you pay interest on.
Is your payment affordable?
Enter your gross annual income and the calculator shows the payment as a share of it. A widely used planning guideline is to keep total student loan payments under roughly 8%โ10% of gross income; much above that and the payment competes with rent, retirement saving and emergency savings. If the number comes out high, the levers are a longer term (lower payment, more total interest), an income-driven federal plan, or refinancing.
Refinancing: the trade-off that isnโt only about rate
Refinancing federal loans with a private lender can lower the rate, but it permanently gives up federal protections โ income-driven repayment, deferment and forbearance rights, and eligibility for federal forgiveness programs. Run the numbers here at both rates, then weigh the interest saved against the safety net you would be trading away. Private loans, which carry none of those protections to begin with, are the more clear-cut refinancing candidates.