Loan Payoff Calculator
See how long it will take to pay off a loan at your current payment, and how much time and interest extra payments save
By Waqar Mushtaq · Last updated:
A loan payoff calculator answers two questions about a loan you already have: how long until it's paid off at my current payment, and how much sooner -- and cheaper -- would it be if I paid a little extra each month? Enter what you still owe, the interest rate, your monthly payment, and an extra amount you're considering, and you get the payoff time and total interest both ways, the time and interest an extra payment saves, a chart of the two balances side by side, a comparison of several extra-payment amounts, and the full month-by-month schedule. It works for any fixed-rate installment debt -- auto loans, student loans, personal loans, or a mortgage's principal and interest.
How Loan Payoff Time Is Calculated
O(n) in the number of paymentsn = number of monthly payments · B = remaining balance · P = monthly payment · r = APR ÷ 12
The same thing month by month: interest on the remaining balance, then the payment
Each month, interest is charged on whatever balance is left (the APR divided by 12), and your payment covers that interest first; everything else reduces the principal. The closed-form formula above solves for how many payments that takes. Its result is rarely a whole number -- the fraction is a smaller final payment -- so this calculator runs the actual month-by-month schedule, rounding interest to the cent each month, and the last payment is just what's left.
Example: $20,000 left at 7% APR, paying $400 a month. r = 0.07 / 12 ≈ 0.005833, so n = −ln(1 − 0.005833 × 20,000 / 400) / ln(1.005833) ≈ 59.3 → 60 payments, with $3,715.28 of interest. Adding $100 a month (P = $500) gives n ≈ 45.7 → 46 payments and $2,841.25 of interest -- 14 months sooner and $874.03 less interest.
Why extra payments help so much: every extra dollar goes straight to principal, so it stops accruing interest for the rest of the loan. That's also why the savings are largest early in a loan, when the balance (and the interest charged on it) is highest.
If the payment doesn't cover the interest (P ≤ r × B), the balance never shrinks and there's no payoff date -- the calculator tells you when that happens.
This calculator assumes a fixed rate, no new borrowing, and that extra payments are applied to principal. If you want the payment for a new loan instead of the payoff time for an existing one, use the Loan Payment Calculator.
Use Cases
Deciding whether to pay extra
See exactly how many months and how much interest an extra $50, $100, or $500 a month saves before committing to it -- the comparison table shows several amounts at once.
Finding your payoff date
Take the balance and payment from your latest statement and see the month your final payment lands, plus the full schedule to check against your lender.
Comparing payoff against other goals
The interest saved is effectively a guaranteed return equal to your loan rate. Weigh it against what the same money would earn in savings or investments.
Rounding up payments
Rounding a $437 car payment up to $500 is a $63 extra payment -- enter it to see what that habit is worth over the loan.
Frequently Asked Questions
How do I calculate how long it will take to pay off a loan?
Use n = −ln(1 − r·B/P) / ln(1 + r), where B is the remaining balance, P the monthly payment, and r the monthly rate (APR ÷ 12). Round up to a whole number of payments -- the last one will be smaller. At 0% interest it is simply B ÷ P.
Does paying extra on a loan reduce the interest?
Yes, as long as the lender applies the extra amount to principal. Interest is charged on the remaining balance, so a lower balance means less interest every month after that, and the loan ends sooner. Check with your lender how extra payments are applied -- some apply them to future payments instead of principal unless you ask.
Is there a penalty for paying off a loan early?
Some loans have a prepayment penalty, a fee for paying off all or part of the balance early, usually within the first few years. Paying small amounts of extra principal normally doesn't trigger it, but your loan agreement is the authority -- see the CFPB reference below.
Why does the calculator say my loan will never be paid off?
Your payment is less than or equal to the interest charged each month (APR ÷ 12 × balance), so nothing is left to reduce the principal. You need a larger payment, a lower rate, or a lump-sum payment to start making progress.
Is it better to make one lump-sum payment or extra monthly payments?
For the same total, paying earlier always saves more interest, because the principal stops accruing interest sooner. A lump sum today beats spreading the same amount over the next year -- but a steady extra monthly payment is often easier to sustain.
Methodology
The formula above is implemented as a standalone module covered by unit tests, so its worked examples are re-checked on every change to the site. It is verified against the authoritative sources listed below.
Not financial advice. This calculator is a general informational tool and cannot account for your individual circumstances. See the terms of use.
Maintained by Waqar Mushtaq. Spotted a result that looks wrong? Report it and it becomes a failing test.