Student Loan Payoff Calculator

A student loan is just an amortizing balance with a servicer logo

Federal and private student loans look special because of IDR, deferment, and forgiveness headlines. The core math on a standard repayment plan is ordinary amortization: a fixed payment, a rate, and a shrinking balance. This student loan payoff calculator shows that payment and what happens if you send more than the bill.

The inputs that matter are the current payoff amount (not the original disbursement), the interest rate on the statement, and the years left—not the years you originally signed.

How extra principal changes the calendar

Interest accrues on the remaining principal. A $100 extra payment this month is $100 that will not sit in the balance next month. Over a decade that compounds as skipped interest, not as a mystery bonus from the Department of Education.

If the extra amount does not cover this month’s interest, the loan is not paying down. Raise the payment or the extra field until the model shows a payoff date.

How to use this calculator

Pull the current balance and rate from the servicer. Set years to the remaining term on a standard plan, or to the term you are considering if you refinance privately. Add the extra dollars you can actually send every month—not a one-time tax refund.

Then open the 401(k) or IRA calculator if the competing use of that $100 is retirement. The honest comparison is the loan rate versus a guaranteed match or a realistic after-tax return, not a 12% stock-market wish.

What this page will not decide for you

Public Service Loan Forgiveness, teacher cancellation, and disability discharge sit outside this model. Recertifying IDR can drop the payment below amortizing and extend the clock. If your strategy is forgiveness, a lower payment can be the point—this tool will look “worse” because it assumes you want the balance gone.

Private refinance resets the rate and usually drops federal protections. Run the new rate here, then read the servicer’s forbearance and death/disability terms before you sign.

Typical examples

Frequently asked questions

How do you calculate a student loan payment?

The same way as any fixed-rate amortizing loan: balance, annual rate, and remaining months. The monthly payment covers that month’s interest first; the rest reduces principal.

Does extra payment go to interest or principal?

On a standard schedule, extra money above the billed payment is applied to principal (confirm with your servicer). That lowers next month’s interest and shortens the calendar.

Can I model income-driven repayment here?

No. IDR uses AGI, family size, and poverty guidelines. This page is for people comparing a level payment vs paying extra on a known rate and balance.

Should I pay extra or invest?

If the loan rate is high and interest is not deductible for you, extra principal is a guaranteed return equal to that rate. If the rate is low and you have an employer 401(k) match, the match usually wins first.

What if I have several federal loans?

Use a weighted average rate, or run each loan. Extra dollars should hit the highest rate first unless your servicer is applying them in a different order.