Figures are estimates based on a fixed rate and consistent monthly payments. Real loans may compound differently or include fees — check your loan agreement for exact terms.
What is a loan payoff calculator?
A loan payoff calculator works out two things your loan statement usually doesn't show clearly: the exact date your balance reaches zero, and how much of your money goes to interest rather than to the debt itself.
You enter your current balance, your interest rate, and what you pay each month. It then simulates the loan month by month — charging interest, applying your payment, and repeating until the balance is gone. The value of doing it that way is that it can also show what happens when you pay more than the minimum, which is the question most people actually came to answer.
It works for any fixed-rate installment loan: personal loans, student loans, car loans, and mortgages.
How this calculator works
It runs a real month-by-month amortization schedule rather than a single formula, which is why it can handle extra payments correctly.
Interest is charged first
Each month your balance is multiplied by your APR divided by 12. That amount is added to what you owe before your payment is applied.
Your payment splits
Whatever is left of your payment after covering that month's interest goes to principal — the part that actually shrinks the debt.
The loop repeats
A smaller balance means less interest next month, so more of your payment goes to principal. This is why progress accelerates near the end.
Why extra payments work so well
Every extra dollar goes straight to principal, so it removes not just that dollar of debt but all the future interest that dollar would have generated.
A $15,000 loan at 6.5% APR with a $400 monthly payment:
Now add just $100/month — a 25% larger payment:
That's 10 months earlier and $399 less interest. You'd hand over $16,414 in total instead of $16,813 — paying more each month, but less overall.
The higher your interest rate, the more dramatic this effect. At 6.5% an extra payment is helpful; at 20%+ it's transformative — which is why credit card debt should usually be attacked before a low-rate car or student loan.
Before you start overpaying
Confirm extra payments go to principal
Some lenders default to applying extra money as a prepayment of your next scheduled payment rather than as a principal reduction. That does almost nothing for your total interest. Most servicers let you specify "apply to principal" online or by note — worth checking before you send anything.
Check for prepayment penalties
Rare on personal and student loans, but they still exist on some mortgages and auto loans. The penalty is usually a percentage of the remaining balance or a set number of months' interest. Your loan agreement will say.
Compare against your other options
Paying off a 4% loan early is a guaranteed 4% return. That's genuinely good. But if you're carrying a 22% credit card, or you have no emergency fund, or you're leaving employer 401(k) matching on the table, those usually come first.
Common questions
The things people usually want to know before trusting a number like this.
Does paying extra always save money?
On any loan with simple interest and no prepayment penalty, yes — every extra dollar toward principal permanently removes the future interest that dollar would have accrued. The exception is precomputed-interest loans, where the total interest is fixed at signing. These are uncommon but do appear on some subprime auto loans, so check your paperwork if the loan came from a dealership.
Is it better to pay extra monthly or one lump sum a year?
Monthly wins, because each payment starts reducing your balance sooner and the effect compounds. Paying $100 extra every month beats paying $1,200 once each December — though the difference is usually modest, so a once-a-year bonus payment is far better than nothing.
What does APR actually mean here?
APR is your annual rate. This calculator divides it by 12 to get a monthly rate, which is how most consumer loans work. Note that APR on a mortgage can also include some fees, so the APR shown on your disclosure may run slightly higher than the interest rate used to calculate your payment.
Why does the calculator say “100+ yrs” sometimes?
Because your payment doesn't cover the interest accruing each month, so the balance grows instead of shrinking — the loan mathematically never pays off. The calculator caps the simulation at 100 years rather than showing a misleading number. Raise the monthly payment above the monthly interest charge and you'll see a real payoff date.
Should I refinance instead of paying extra?
They aren't mutually exclusive, and refinancing to a lower rate then keeping your old payment amount is often the strongest combination. Weigh any closing costs against the interest saved, and be careful about resetting a nearly-paid-off loan back to a fresh 30-year term.
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