Student Loan Payoff & Refinance Calculator

Why a small extra payment early beats a large one late

Every extra dollar you send goes to principal, and principal you have already removed never accrues interest again for the entire remaining life of the loan. That is why the payoff time is not linear in the extra amount, and not linear in when you start either. A hundred dollars a month starting now is not half as effective as two hundred a month starting now; it is far more than half as effective, and it is enormously more effective than two hundred a month starting in five years, even though the second plan sends more total money to the servicer.

The reason is that early principal reductions compound their own effect. Removing a thousand dollars of principal in year one removes the interest that thousand would have generated in year one, year two, and every year to the end. The saved interest is not paid, which means next month's interest is calculated on a smaller balance, which means slightly more of the ordinary minimum payment goes to principal too, which shrinks the balance a little faster again. Each of those effects is small on its own; over a decade they are the difference between the second and third columns above.

The practical consequences are worth stating plainly. First, the best time to start an extra payment is the month you can afford it, not the month you feel financially ready — waiting a year to start a larger contribution usually loses to starting a smaller one immediately. Second, a windfall applied now is worth more than the same windfall applied later, so a tax refund or a bonus put against the balance early is doing more work than its size suggests. Third, consistency matters more than size, because an extra payment made every month gets the compounding effect every month.

There are two servicer mechanics that can quietly undo all of it, and they are worth checking before you set up a standing transfer. Extra money is not always applied to principal by default: many servicers will treat a payment larger than the amount due as a prepayment of the NEXT instalment, advancing your due date rather than reducing your balance. That feels helpful and does nothing for your interest. Tell the servicer in writing that additional amounts are to be applied to principal, and check the following statement to see that it was. The second mechanic is allocation across multiple loans: if your balance is several loans in one account, extra money is often spread across all of them proportionally rather than aimed at the highest rate, which is the least useful thing it could do. Direct it at the highest-rate loan explicitly. This calculator models a single blended balance at a single rate, so it cannot see either of these; it assumes every extra dollar reaches principal on the day it is paid.

When the minimum payment never gets you anywhere

If your minimum payment is at or below the interest accruing each month, the loan does not have a long payoff time. It has none. The balance grows every month you pay exactly as agreed, and it will keep growing for as long as that arrangement holds. This page reports that as its own outcome rather than as a very large number of months, because a month count in that situation is not an answer — it is whatever the calculator's iteration limit happened to be, dressed up as arithmetic. When you see it, the number you need is not a payoff date but the payment that would start reducing the balance at all, which is anything above the monthly interest: the balance multiplied by the annual rate, divided by twelve.

This situation is more common than it sounds, and it is not always a mistake. Some repayment arrangements deliberately set a payment below the accruing interest for a period, on the understanding that the shortfall is either subsidised or added to the balance later. Growing balances also show up during a graduated repayment period, during forbearance, and whenever a borrower is paying a fixed token amount while income recovers. What makes it dangerous is unpaid interest being capitalized — added to principal — at the end of such a period, because from that moment the interest starts earning interest, and the loan you owe is larger than the loan you borrowed. This calculator does not model any capitalization event; it assumes the balance you enter is the balance today and that no unpaid interest is ever rolled into it.

A second thing this calculator will not do is invent a payoff date for a schedule that technically amortizes but takes longer than a century. A payment one dollar above the monthly interest does eventually clear the loan, in the same sense that a dripping tap eventually fills a reservoir. Reporting that as a number of years would be technically true and practically worthless, so it is reported as its own outcome too. Between them, these two rules mean every figure this page shows you comes from a schedule that actually finishes.

A lower monthly payment is not a cheaper loan

The most common way a refinance quote misleads has nothing to do with the rate. It is the term. Stretching the same balance over more years lowers the monthly payment arithmetically, whatever happens to the rate, and a quote that leads with the new monthly figure is inviting you to read a longer term as a discount. It is not one: you pay interest for every year the loan exists, so more years at a lower rate can easily cost more in total than fewer years at a higher one. This page flags that case explicitly rather than letting the monthly figure carry the argument, and the interest row will show a negative saving when it happens.

That does not make a longer term wrong. A lower required payment has real value if it is the difference between meeting your obligations comfortably and living one bad month away from a missed payment, and buying that breathing room with additional interest can be an entirely rational purchase. The point is to know the price. Refinancing to a longer term and then voluntarily paying the old, higher amount each month gets you both the lower obligation and the shorter payoff, which is often the best available structure — run that case here by entering the refinance and putting the difference in the extra payment field.

Two things this calculator does not include are worth naming. It applies no origination or application fee to the refinance, so a quote that carries one is slightly better on this page than in life; add any such fee to the balance before comparing if you want the honest figure. And it assumes a fixed rate throughout. A variable-rate refinance offer will usually quote a starting rate below any fixed alternative, and that rate is not a promise — modelling it as fixed here would understate its cost in any environment where rates rise. If the offer in front of you is variable, run this page at the highest rate the contract permits, not the one on the marketing page, and see whether the comparison still favours it.