Student Loan Payoff Calculator
See exactly when your student loans disappear, what they cost in total, and how much an extra payment each month really saves.
Last updated: October 2026
Loan details
How student loan payoff works
Each month, interest accrues on your remaining balance first, and whatever is left of your payment reduces the principal. Because interest is charged on a shrinking balance, a fixed payment pays off more principal every month: early payments are interest-heavy, later ones are almost all principal. There is no closed-form shortcut the calculator hides: it simulates month by month, applying interest, then your payment, until the balance hits zero.
The critical threshold is the monthly interest charge: balance times the monthly rate. If your payment is smaller than that number, the balance grows instead of shrinking and the loan never pays off. The calculator warns you if that is the case, because income-driven plans can put borrowers in exactly that position.
Worked example
Take a $25,000 balance at 6.8% APR with a $300 monthly payment. The monthly interest at the start is $25,000 times 0.068/12 = $141.67, so $158.33 of the first payment hits principal. Month by month, the loan pays off in 114 months (9 and a half years) with $8,929 in total interest: the degree really costs $33,929.
Now add an extra $100 a month ($400 total). The loan pays off in 78 months with $5,950 in total interest. That extra $100 a month saves $2,980 in interest and erases 36 months, a full 3 years, of payments. Small, consistent overpayments beat occasional lump sums because every extra dollar immediately stops earning interest against you.
Avalanche vs. snowball: which loan first
With multiple loans, two strategies compete. The avalanche method aims every extra dollar at the highest interest rate first: it minimizes total interest, mathematically optimal. The snowball method aims at the smallest balance first: you clear whole loans faster, which keeps motivation up. The interest difference between them is usually small (a few hundred dollars on typical balances), so pick the one you will actually follow for years. Either beats spreading extra payments evenly across all loans.
Federal vs. private loans
Federal loans offer income-driven repayment, deferment, forbearance, and forgiveness programs (like Public Service Loan Forgiveness) that private loans do not. They have no prepayment penalty. Private loans sometimes offer lower rates to strong borrowers but come with fewer safety nets. The golden rule of refinancing: refinancing private loans to a lower rate is usually smart, but refinancing federal loans into private ones permanently gives up federal protections, so only do it for a large rate saving with stable income.
Tips for paying off faster
Automate the extra payment. A separate automatic transfer labeled "principal only" beats willpower. Tell your servicer explicitly that extra payments apply to principal, not to advancing your due date.
Attack the highest rate first. List every loan with its rate and balance, then point all extra money at the top rate while paying minimums elsewhere.
Throw windfalls at principal. Tax refunds, bonuses, and side income applied to principal in one shot can shave months off, because they skip the slow drip of monthly interest entirely.
Recertify income-driven plans on time. Missing the annual recertification can capitalize unpaid interest and raise payments. Set a calendar reminder every year.
Student Loan FAQs
How do extra payments shorten a student loan?
Every extra dollar goes straight to principal, which shrinks the balance that future interest is charged on. That compounding effect is why a modest extra payment, like $100 a month, can erase years from a loan and save thousands in interest.
Should I pay extra on my student loans or invest the money?
Compare your loan's interest rate to your expected investment return. Paying down a 7% loan is a guaranteed 7% return, which beats most conservative investments. Below about 4 to 5%, investing often wins mathematically, though being debt-free has real psychological value.
Is there a prepayment penalty on federal student loans?
No. Federal student loans have no prepayment penalty, so you can always pay extra. Most private student loans also allow extra payments without penalty, but check your promissory note to be sure.
Should extra payments go to the highest-rate loan first?
Mathematically, yes: the avalanche method (highest rate first) minimizes total interest. The snowball method (smallest balance first) costs a bit more but gives faster psychological wins. Pick the one you will actually stick with.
What happens if my payment does not cover the monthly interest?
The balance grows instead of shrinking, a situation called negative amortization. On income-driven plans this can happen by design, with unpaid interest sometimes capitalizing. The calculator above will warn you if your payment is too low to ever pay the loan off.
How does interest capitalization work on student loans?
Unpaid interest can be added to your principal (capitalized), after which you pay interest on the interest. This typically happens when a deferment or forbearance ends, or when you leave an income-driven plan. Capitalization is why pausing payments is more expensive than it looks.
Is refinancing student loans a good idea?
Refinancing private loans to a lower rate is usually smart. Refinancing federal loans into private ones is riskier: you permanently lose income-driven repayment, deferment options, and any future forgiveness programs. Only do it if the rate savings are large and your income is stable.
How do I make sure extra payments reduce principal?
Tell your servicer explicitly that extra payments should apply to principal, not advance your due date. Many servicers default to pushing the next due date forward, which does not save interest. Check your statements to confirm the extra went to principal.