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Loan Payoff Calculator

Q: Will my lender automatically apply extra payments to principal?

Not always. Many lenders apply extra amounts to your next scheduled payment by default rather than directly reducing principal, unless you specifically mark the extra amount as an additional principal payment. Always confirm with your loan servicer.

Q: Are there prepayment penalties?

Some loans, particularly certain personal loans and a small number of auto loans, charge a prepayment penalty. Check your loan agreement before making large extra payments. Most mortgages, federal student loans, and modern auto loans do not have prepayment penalties.

Q: Does this model income-driven student loan repayment?

No. This calculator assumes a standard fixed-rate, fixed-term amortizing loan and does not model income-driven repayment plans, forgiveness programs, or interest subsidies used by some federal student loans.

For auto, personal, or student loans. Enter your loan details, then add an optional extra monthly payment to see side-by-side how much time and interest you'd save.

Loan Details

Loan balance ($)

Interest rate (% APR)

Remaining term (months)

Extra payment per month ($) — optional

How extra payments save you money

Every extra dollar you pay toward a loan goes straight to reducing your principal balance — it isn't split between principal and interest like your regular payment is. A smaller principal balance means less interest accrues the following month, which means more of your next regular payment also goes to principal. This compounding effect is why even modest extra payments (an extra $50-100/month) can shave years off a loan and save meaningful interest, especially early in the loan term when the balance — and therefore the interest accruing on it — is at its highest.

How the payoff is calculated

Your regular payment is derived from the standard fixed-rate amortization formula used across the lending industry:

M = P × [ r(1+r)ⁿ ] / [ (1+r)ⁿ − 1 ]

Where P is the loan principal, r is the periodic (monthly) interest rate — the annual rate divided by 12 — and n is the total number of monthly payments. To build the payoff schedule, the calculator then applies that payment month by month: each month it charges interest on the current balance (balance × r), subtracts that interest plus any extra payment from the balance, and repeats until the balance reaches zero. Any extra amount you enter is applied entirely to principal, which is why it shortens the term and reduces total interest. This is the same period-by-period method used in a full amortization schedule, and the mechanics are walked through in how mortgage amortization works.

Methodology reference: the amortization formula above is the standard closed-form solution for a fixed-rate installment loan. For a plain-language explanation of amortization from a regulator, see the U.S. Consumer Financial Protection Bureau's definition of an amortized loan (consumerfinance.gov). All calculations run locally in your browser; no figures are sent to a server.

Which loans is this calculator for?

This is a general-purpose amortizing loan calculator, so it works for:

Auto loans — typically 3-7 year terms, fixed rate.
Personal loans — typically 2-7 year terms, used for debt consolidation, home improvement, or other expenses.
Student loans — federal and private student loans with a fixed rate amortize the same way (though federal loans have their own income-driven repayment options this calculator doesn't model — see the FAQ below).

For a mortgage specifically — with property tax, insurance, and PMI — use the mortgage calculator instead.

Frequently asked questions

Will my lender automatically apply extra payments to principal?

Not always — this depends on your loan servicer. Many lenders apply extra amounts to your next scheduled payment by default rather than directly reducing principal, unless you specifically mark the extra amount as "additional principal payment." Always confirm with your loan servicer that extra payments are being applied the way you intend, or you won't see the payoff acceleration this calculator shows.

Are there prepayment penalties?

Some loans — particularly certain personal loans and a small number of auto loans — charge a prepayment penalty for paying off the loan early or making large extra payments. Check your loan agreement before making large extra payments. Most mortgages, federal student loans, and modern auto loans do not have prepayment penalties, but it varies.

Does this model income-driven student loan repayment?

No. Federal student loans have income-driven repayment (IDR) plans where your payment is based on income rather than a fixed amortization schedule, and some plans include forgiveness after a set number of years. This calculator assumes a standard fixed-rate, fixed-term amortizing loan — it does not model IDR plans, forgiveness programs, or interest subsidies. If you're on or considering an IDR plan, use your loan servicer's tools or the Department of Education's official calculators instead.

Is my loan information uploaded anywhere?

No. Every calculation happens locally in your browser using JavaScript. Your loan balance, rate, and payment amounts are never sent to a server.

Related guides

Debt avalanche vs. debt snowball — which payoff order to use when you have multiple debts.
How extra payments save interest — a worked example of extra-payment savings.

Not financial advice. This calculator provides an estimate for general informational purposes only, based on a standard fixed-rate amortization schedule. It does not account for prepayment penalties, income-driven repayment plans, loan forgiveness programs, deferment/forbearance, or your specific lender's rules for applying extra payments. Consult your loan servicer or a financial advisor before making decisions based on these figures.