Mortgage Payoff Calculator
Find out how much faster you could be mortgage-free. Combine any mix of extra monthly payments, an extra yearly lump sum, a one-time payment now, and switching to biweekly payments, then see exactly how many months and how much interest you save versus your current schedule. Enter your balance and years remaining, or use your monthly payment if you do not know the term. You can also solve for the extra payment needed to hit a target payoff date.
Formula
Worked example
A $250,000 balance at 6.5% with 25 years left has a scheduled payment of about $1,688. Adding $200 a month pays it off roughly 5 years and 6 months (66 months) sooner and saves around $65,000 in interest, about a 19% cut. Stack a $5,000 one-time lump sum on top and you shave off even more. To clear it in 15 years instead, the calculator solves that you would need to pay about $490 extra each month.
How extra payments pay off a mortgage faster
Your scheduled payment is fixed by the original balance, rate and term, and each month it is split between interest on the current balance and principal that reduces it. When you add an extra amount, that whole extra goes to principal, so the balance falls faster than the schedule expects. A smaller balance means less interest is charged the next month, which frees up even more of every future payment to attack the principal, a compounding effect that snowballs over time.
Combine four payoff strategies at once
Unlike calculators that make you pick a single tactic, this one lets you stack any mix of four. Extra each month adds a fixed amount to every payment. Extra once a year applies a single lump sum every twelve months, handy if you overpay from a bonus or tax refund. A one-time lump sum applies a single payment now, for example from savings or an inheritance, and is the most front-loaded because it removes principal that would have accrued interest for the longest. Biweekly payments split your monthly payment in half and pay it every two weeks; because there are 52 weeks in a year, you make 26 half-payments, which equals 13 full monthly payments, one more than the 12 a standard schedule expects. That single extra payment a year is enough to shave years off a long loan, and you can layer it on top of the others.
Solve for a target payoff date
If you have a date in mind rather than an amount, turn on "solve for a target payoff date" and enter the number of years you want to be debt-free in. The calculator works backward and finds the smallest fixed extra monthly payment that clears the loan within that window, using a binary search over the payoff simulation. This is the reverse of the usual question: instead of asking how much sooner a given overpayment finishes the loan, it tells you exactly what overpayment a given deadline requires.
Two ways to enter your loan
If you know how many years are left, choose "balance and years remaining" and the calculator derives your scheduled payment. If you have lost track of the term but know your monthly principal and interest payment, choose "balance and monthly payment" and it solves for the remaining term instead. Either way the math is the same: the loan is simulated month by month once on its current path and once with your chosen strategy, and the difference is reported.
Reading the results
Time saved is how many months sooner the balance reaches zero. Interest saved is the reduction in total interest paid over the life of the loan, and the percentage shows that saving relative to the interest you would otherwise pay. Total paid with and without the strategy lets you compare the full out-of-pocket cost of each path. The figures assume a fixed rate and that every extra payment is applied to principal. The balance chart and the annual schedule below break the loan down year by year so you can see exactly when it clears.
Payoff strategies at a glance
| Strategy | How it works | Best when |
|---|---|---|
| Extra each month | A fixed amount added to every payment | You have steady spare cash flow |
| Extra once a year | A lump sum every 12 months | You overpay from a bonus or refund |
| One-time lump sum | A single payment applied now | You have savings to deploy today |
| Biweekly payments | Half-payment every two weeks (13/year) | You want one extra payment painlessly |
How the four strategies in this calculator differ. They can be combined. Savings depend on your balance, rate and term.
Frequently asked questions
Can I combine extra monthly, yearly and lump-sum payments?
Yes. This calculator lets you stack all four strategies at once: an extra monthly amount, an annual lump sum, a one-time payment now, and biweekly payments. The simulation applies every extra to principal in the right month, so you see the combined effect on payoff time and total interest, not just one tactic in isolation.
How do biweekly mortgage payments pay off the loan early?
Paying half your monthly amount every two weeks means 26 half-payments a year, which equals 13 full payments instead of 12. That one extra payment a year goes to principal and can clear a 30-year loan several years early. Confirm your lender applies the half-payments rather than holding them.
How do I find the extra payment needed to pay off by a certain date?
Turn on "solve for a target payoff date" and enter the number of years you want left. The calculator searches for the smallest fixed extra monthly payment that clears the balance within that window and reports it, along with the interest you would save.
Is a one-time lump sum or a monthly overpayment better?
A lump sum applied early usually saves the most interest per dollar because it removes principal that would otherwise accrue interest for the longest. A monthly overpayment is easier to sustain and still compounds well. Try both, or combine them, in the calculator to compare the time and interest each saves.
Does an extra payment go entirely to principal?
It should, but confirm with your lender. To shorten the term you want overpayments applied to principal rather than held toward your next scheduled payment. Some lenders need you to specify this explicitly.
Are there penalties for paying off a mortgage early?
Some mortgages charge early-repayment or prepayment penalties, often during a fixed-rate period or the first few years. Check your loan agreement before committing to large or frequent overpayments.