How Student Loan Payments Work
Student loans use standard amortization: each monthly payment covers the interest that accrued since the last payment, with the remainder reducing the principal. Early in the repayment period, most of the payment goes toward interest; as the balance falls, more goes toward principal. The monthly payment amount is calculated using the same formula as any installment loan: PMT = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the principal, r is the monthly interest rate, and n is the number of payments.
The Grace Period and Unsubsidized Loans
Federal student loans typically have a 6-month grace period after graduation, leaving school, or dropping below half-time enrollment before payments are required. How this period affects your balance depends on the loan type:
- Subsidized loans: The government pays the interest that accrues during in-school periods and the grace period. Your balance when repayment begins equals what you originally borrowed.
- Unsubsidized loans: Interest accrues from the moment the loan is disbursed. During the grace period, 6 months of interest adds to your balance (a process called capitalization). On a $35,000 loan at 6.54%, that is approximately $1,140 of additional balance before your first payment.
Federal Repayment Plans
Federal student loans offer several repayment plan options:
- Standard (10 years): Fixed payments, highest monthly cost, lowest total interest. The default plan and usually the best choice for minimizing total cost.
- Extended (up to 25 years): Lower monthly payment, significantly more interest paid over life of loan.
- Income-Driven Repayment (IDR): Payments set at 5–10% of discretionary income under plans like SAVE, IBR, PAYE, or ICR. Remaining balance may be forgiven after 10–25 years, though forgiven amounts may be taxable income.
- Public Service Loan Forgiveness (PSLF): Forgives remaining balance after 10 years (120 payments) for borrowers working in qualifying public sector or nonprofit jobs while on an IDR plan.
The Power of Extra Payments
Making even modest extra payments has an outsized impact on total interest and payoff time. An extra $100/month on a $35,000 loan at 6.54% over 10 years reduces total interest by approximately $1,400 and pays off the loan more than a year early. Extra payments go directly to principal, which reduces the balance on which future interest is calculated — an accelerating effect. Use the "Extra monthly payment" field in this calculator to see exactly how much each additional dollar saves.
Should You Pay Off Student Loans Early?
The right answer depends on your interest rate and alternative uses of the money. If your loans carry a rate above 6–7%, paying them off aggressively is often mathematically equivalent to or better than investing in a bond fund. If your rate is under 5%, especially after a tax deduction for student loan interest (up to $2,500/year for eligible borrowers), you might generate higher returns by investing the extra money in a diversified equity portfolio. There is also a behavioral benefit to eliminating debt: lower financial stress and improved cash flow flexibility can be worth more than the marginal difference in expected return.