Student Loan Payoff Calculator
Paying more than the scheduled amount does one thing: it reduces the balance faster, so less interest accrues on it. The calculator below simulates the loan month by month with your extra payment applied, and reports how many months earlier it clears and roughly how much interest that avoids.
The result usually surprises people, because the saving compounds. Every dollar of principal removed early is a dollar that stops generating interest for the whole remaining term.
What does paying extra do?
Enter the extra amount you would add each month on top of the scheduled payment.
Tell your servicer where the extra money goes
This is the single most important thing on the page, and it is the step most borrowers miss. An extra payment is not automatically applied to principal. Many servicers treat anything above the scheduled amount as an advance payment — it satisfies next month's bill, moves the due date forward, and leaves the balance broadly where it was. You get a "paid ahead" status instead of a smaller loan.
The result the calculator shows only happens if the extra is applied to principal, so instruct the servicer explicitly and in writing to apply overpayments to principal without advancing the due date. Then check the next statement to confirm the balance moved by the amount you expected. If you hold several loans with one servicer, also say which loan the extra should go to, or it may be spread across all of them.
Federal student loans carry no prepayment penalty, so paying early never costs a fee. Some private loans differ — check before committing.
Why a small extra payment does so much
The saving comes from two directions at once. The balance falls faster, so each subsequent month accrues less interest, and the term shortens, so there are fewer months of interest in total. Those effects reinforce each other, which is why the months saved usually grow faster than the extra amount.
Timing matters as much as size. The same extra payment applied in year one removes principal that would otherwise have accrued interest for the entire remaining term; applied in the final year, it removes principal that had almost finished costing you anything. If your capacity to overpay is limited, front-loading it is worth considerably more than spreading it evenly.
When the payment is too small to work
The calculator refuses to produce an answer if the payment does not exceed the monthly interest, and that case is worth understanding rather than treating as an error. If the interest charged each month is larger than the payment made, the unpaid part is added to the balance and the loan grows despite the payments — negative amortisation.
This happens with high-rate private debt on a minimum payment, and it can happen on income-driven federal plans where a low required payment does not cover accruing interest. It is not always a mistake to be in that position, since income-driven plans exist precisely for people who cannot afford more, but you should know which situation you are in. The remedy is either a larger payment or a different plan, not a longer wait.
Which loan to overpay first
Most borrowers hold several loans, and the extra payment should go to one of them rather than being spread thinly. Two approaches dominate, and they optimise for different things.
- Highest rate first (the avalanche). Mathematically optimal — it removes the most expensive debt first and minimises total interest. Run each loan through the calculator separately to see which is genuinely costing most.
- Smallest balance first (the snowball). Slightly more expensive in total, but it clears whole loans quickly, which reduces the number of payments to track and gives visible progress. For people who have abandoned repayment plans before, the one they stick to is the better one.
- Anything not on an income-driven plan or a forgiveness track, first. Overpaying a loan you expect to have forgiven reduces the amount forgiven, not the amount you pay.
- Variable-rate private loans before fixed-rate federal ones, when rates are rising — the exposure is open-ended and the federal protections are not worth giving up.
A realistic way to find the extra money
The calculator will happily accept an extra payment you cannot sustain. A figure you keep up for three months and then abandon does less good than a smaller one you maintain for years, because the benefit depends on removing principal early and continuously.
Two habits work better than a heroic monthly number: round the payment up to a convenient figure and leave it there, and direct one-off money — a tax refund, a bonus, the first month of a raise — straight at principal before it is absorbed into ordinary spending. Run the raise calculator first if you want to see what an increase is worth in monthly terms; that difference is often the most painless source of an overpayment.
Frequently asked questions
It depends on the balance, rate and how much extra you add, which is what the calculator works out. The saving compounds — each dollar of principal removed early stops accruing interest for the whole remaining term, so the months saved usually grow faster than the extra amount does.
Often not. Many servicers treat an overpayment as an advance on next month, moving the due date forward and leaving the balance largely unchanged. Instruct them in writing to apply overpayments to principal without advancing the due date, then confirm on the next statement.
Federal student loans have no prepayment penalty, so early repayment never incurs a fee. Some private loans have different terms, so check the agreement before committing to a payoff plan.
Highest rate first minimises total interest and is mathematically optimal. Smallest balance first clears loans faster and is easier to sustain. The best choice is the one you will actually keep doing — and neither applies to a loan you expect to have forgiven.
Because the payment is smaller than the interest accruing each month, so the unpaid interest is added to the balance and the loan grows. That is negative amortisation. It needs a larger payment or a different repayment plan; waiting makes it worse.