S
StudentPayoff

Pay off your student loans faster

See exactly how many months until you're debt-free, what an extra payment saves, and which refi lenders fit your situation. Free, instant, no signup.

Loan details

$
%
$
$
Every dollar above the scheduled payment goes straight to principal.
Time to debt-free
9 yr 11 mo
Payoff date: Apr 2036

Principal vs interest

Total paid$47,565
  • Principal$35,000
  • Interest$12,565
Total interest
$12,565
Total paid
$47,565
Balance
$35,000
Months
119

How the payoff math works

Every month, your student-loan balance accrues interest at your annual rate divided by 12 (the periodic monthly rate). Whatever you pay above that month's interest charge goes straight to principal — that's the part that actually reduces your balance.

Mathematically, the months-to-payoff is the smallest n for which simulating n months of payments against the balance brings it to zero. The closed-form for a fixed payment M, balance P, and monthly rate r is:

n = -log(1 - (P × r / M)) / log(1 + r)

We simulate it month-by-month instead so we can also handle extra payments and the “insufficient payment” edge case (when M ≤ Pr — the balance grows forever and there is no payoff).

Total interest is the sum of every month's interest charge across the simulation — i.e., (total paid) − (original balance).

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Frequently asked questions

How is my student-loan payoff date calculated?

We use the standard fixed-rate amortization formula your servicer uses. Each month, interest accrues on the remaining balance at your annual rate divided by 12. Whatever's left of your monthly payment after the interest charge goes to principal. We simulate this month-by-month, including any extra payments, until the balance hits zero — and that's the month count you see.

Does paying extra each month really save that much?

Yes, especially on higher-rate loans. Every dollar above the scheduled payment goes 100% to principal, which reduces the balance interest accrues on for every future month. On a $35,000 loan at 6.5% with a $400/mo payment, even an extra $100/mo saves around $3,000 in interest and shaves nearly two years off the loan.

Should I pay off student loans early or invest instead?

If your loan rate is 6%+ and you don't have an emergency fund or 401(k) match, paying down the loan is often the better risk-adjusted move. If you have low fixed-rate federal loans (under 5%) and you're confident you can earn more than that in a long-term diversified portfolio, the math sometimes favors investing. Most people benefit from a hybrid: capture the 401(k) match first, build a starter emergency fund, then attack high-rate debt.

Should I refinance my federal student loans?

Only if you're confident you won't need federal protections like PSLF, IDR, or extended forbearance. Refinancing converts federal loans to private permanently — there's no way back. Run the numbers on our refinance calculator, but factor in the value of the protections you'd be giving up.

Is this calculator accurate for my real loans?

The math is exact for fixed-rate loans (the vast majority). Your actual servicer may apply payments slightly differently — for example, applying overpayments to interest before principal unless you specify otherwise. If you make extra payments, always log into your servicer and confirm the extra was applied to principal.

What's the difference between snowball and avalanche?

Avalanche pays the highest-rate loan first (mathematically optimal — saves the most interest). Snowball pays the smallest balance first (psychologically optimal — quickest emotional wins). Use our snowball-vs-avalanche comparator to see how much money the difference is for your specific portfolio.