How much faster does an extra payment actually clear a student loan?

It depends on the balance and rate, but the effect is consistently large relative to the extra amount. On a 45,000 balance at 5.0%, adding 150 a month to a 480 base payment cuts the payoff time from 10 years to about 7 years and 1 month and saves roughly 3,650 in interest.

Should I pay off the loan with the highest balance or the highest rate first?

Rate first, in almost every case, because interest accrues on each loan's own balance at its own rate. Directing extra payments at the highest-rate loan while paying the minimum on the rest reduces total interest more than spreading extra payments evenly or targeting the largest balance.

Does this calculator account for income-driven repayment plans?

No. It assumes a fixed payment every month until the balance reaches zero. Income-driven plans recalculate the required payment annually against income and household size, and can end in loan forgiveness of a remaining balance, both of which this straight-line amortization cannot model.

What interest rate should I use for a private student loan with a variable rate?

Use the rate shown on your most recent statement, not the rate at origination, and re-run the calculator whenever the index it is tied to moves. Variable-rate private loans reprice periodically, so a payoff date calculated once at the starting rate will drift as the underlying index changes.

Will my extra payment automatically go toward principal?

Not always. Some servicers apply extra amounts to the next scheduled payment date instead of reducing principal unless you log into the account or call and specifically request that the extra amount be applied to principal only, so confirm this with your servicer after the first extra payment.

Can I still deduct student loan interest if I am paying extra to clear the loan faster?

Yes. The US student loan interest deduction under IRC Section 221 applies to interest actually paid in the tax year, up to 2,500, regardless of whether the payment was the required minimum or included an extra amount, subject to the income phase-out in IRS Publication 970.

Student loan payoff calculator

This calculator turns a balance, a rate and a monthly payment into two dates: when the loan clears at your current payment, and when it clears if you add a fixed extra amount every month. The gap between those two dates, and the interest that never gets charged because of it, is the real payoff for anyone deciding whether to send more than the minimum.

Reading the payoff date against your loan type

A federal Direct Unsubsidized Loan taken out for the 2024-2025 award year carries a fixed rate of 6.53% for undergraduates and 8.08% for graduate borrowers, according to Federal Student Aid's published rate schedule, so a payoff timeline built at 6-8% is realistic for most recent federal borrowers rather than a worst case.

Private loans vary far more widely, often 4% to 15% depending on credit and whether the rate is fixed or variable, so the payoff date this tool returns is only as good as the rate you enter — pull it from your most recent statement rather than the rate printed on the original promissory note if the loan is variable.

A standard 10-year federal repayment plan is the reference point most borrowers compare against. If this calculator returns a payoff date well past ten years from disbursement at your current payment, the payment is below the standard amount and interest is accumulating faster than a default federal schedule would allow.

Three payoff scenarios worth running

A 25,000 balance at 6.8% with a 280 monthly payment clears in about 10 years and 5 months and costs roughly 9,940 in interest. Adding 60 a month brings that down to 8 years, cutting total interest to about 7,430 — a saving of roughly 2,510 for 60 a month sent for a little over six and a half years.

A 45,000 balance at 5.0% with a 480 payment clears in exactly 10 years with about 12,180 in interest. Push the payment up by 150 to 630 and the loan clears in 7 years and 1 month, with interest falling to about 8,530 — a saving of roughly 3,650, and almost three years returned.

A larger 60,000 balance at 7.5% with a 650 payment takes 11 years and 7 months and racks up about 29,740 in interest, because the higher rate compounds against a bigger base. A 200 monthly top-up shortens that to 7 years and 10 months and interest to about 19,390 — a saving of roughly 10,350, the largest of the three because rate and balance are both working against the borrower before the extra payment is applied.

Where the payoff formula stops matching reality

The calculation assumes a constant rate, a constant payment and no forgiveness, deferment or forbearance. It cannot model an income-driven repayment plan, where the required payment is recalculated every year against income and family size and can fall to zero, nor can it model a forgiveness event that erases the remaining balance regardless of what interest has accrued.

It also assumes every extra dollar is applied to the loan the moment it is paid. Some servicers apply extra payments to a future due date instead of the principal unless you specifically request principal-only treatment in writing, which silently turns your accelerated payoff plan back into the standard one.

If you hold several loans with different rates, running this tool loan by loan and directing extra payments at the highest-rate balance first will beat running it once against a blended average rate, because interest is charged loan by loan, not on a combined balance.

Federal, private and tax-year timing differences

Federal loan rates reset every July 1 and then stay fixed for the life of that specific loan, so a borrower with loans from three different years is carrying three different fixed rates, not one blended figure — check the disbursement date on each loan before entering a single average.

Interest on federal loans has, at various points, been paused during administrative forbearance periods that are announced separately from the standard repayment schedule; a payoff date calculated during one of those pauses will look shorter than it will once interest resumes accruing.

In the US, up to 2,500 of student loan interest paid in a tax year can be deducted above the line under Internal Revenue Code Section 221, subject to a modified adjusted gross income phase-out described in IRS Publication 970, which effectively lowers the true cost of interest for many borrowers below the raw figure this calculator reports.

Frequently asked questions

How much faster does an extra payment actually clear a student loan?: It depends on the balance and rate, but the effect is consistently large relative to the extra amount. On a 45,000 balance at 5.0%, adding 150 a month to a 480 base payment cuts the payoff time from 10 years to about 7 years and 1 month and saves roughly 3,650 in interest.
Should I pay off the loan with the highest balance or the highest rate first?: Rate first, in almost every case, because interest accrues on each loan's own balance at its own rate. Directing extra payments at the highest-rate loan while paying the minimum on the rest reduces total interest more than spreading extra payments evenly or targeting the largest balance.
Does this calculator account for income-driven repayment plans?: No. It assumes a fixed payment every month until the balance reaches zero. Income-driven plans recalculate the required payment annually against income and household size, and can end in loan forgiveness of a remaining balance, both of which this straight-line amortization cannot model.
What interest rate should I use for a private student loan with a variable rate?: Use the rate shown on your most recent statement, not the rate at origination, and re-run the calculator whenever the index it is tied to moves. Variable-rate private loans reprice periodically, so a payoff date calculated once at the starting rate will drift as the underlying index changes.
Will my extra payment automatically go toward principal?: Not always. Some servicers apply extra amounts to the next scheduled payment date instead of reducing principal unless you log into the account or call and specifically request that the extra amount be applied to principal only, so confirm this with your servicer after the first extra payment.
Can I still deduct student loan interest if I am paying extra to clear the loan faster?: Yes. The US student loan interest deduction under IRC Section 221 applies to interest actually paid in the tax year, up to 2,500, regardless of whether the payment was the required minimum or included an extra amount, subject to the income phase-out in IRS Publication 970.

Sources

Federal Student Aid — interest rates for Direct Loans — Fixed rates of 6.53% (undergraduate) and 8.08% (graduate) for Direct Unsubsidized Loans first disbursed July 1, 2024 to June 30, 2025.
IRS — Topic no. 456, Student loan interest deduction — Describes the above-the-line deduction of up to 2,500 in student loan interest under IRC Section 221, with income-based phase-out, for the 2024 tax year.