How to use this mortgage payoff calculator
- Describe your mortgage either by the original amount, term and number of payments made, or by the current balance and time left from your latest statement.
- Enter the interest rate on your loan (not today’s market rate). The default is the 7.03% average 30-year fixed rate as of September 24, 2026 (Freddie Mac), rounded to the nearest eighth of a point.
- Choose “Extra payments” and add a monthly, yearly or one-time amount to see your new payoff date and interest saved.
- Or choose “Target payoff date” to find the extra monthly payment that clears the loan by then.
How extra mortgage payments work
Each month, interest is charged on your remaining balance and the rest of your payment reduces principal. Early in a loan most of the payment is interest; as the balance falls, more of it goes to principal. An extra payment that goes straight to principal lowers the balance that every future month’s interest is charged on, so each later payment pays down more principal and the loan ends sooner.
That is why the savings are larger than the extra money itself suggests, and why paying extra early in the loan does the most good. Your required payment doesn’t change; you simply run out of balance before the scheduled end. To see how a regular schedule splits each payment, use the amortization calculator.
Payoff formula
With a fixed extra amount E added to the regular payment M, the number of months left is:
n = −ln(1 − r × B / (M + E)) / ln(1 + r)
- n
- months until the loan is paid off (round up)
- B
- current balance
- M
- regular monthly principal & interest payment
- E
- extra monthly payment
- r
- monthly interest rate = annual rate ÷ 12
Worked example
A $350,000 loan at 7% for 30 years has a payment of M = $2,328.56. After 60 payments the balance is B = $329,461, with 300 payments left. With E = $200 and r = 0.005833: n = −ln(1 − 0.005833 × $329,461 ÷ $2,528.56) ÷ ln(1 + 0.005833) = 245.4, so the last (smaller) payment is month 246. That is 4 years 6 months early, and interest over the rest of the loan falls from $369,107 to $291,058, a saving of $78,049.
Paying off by a target date
To finish in T months, pay the amount that would amortize the balance over T months: MT = B × r ÷ (1 − (1 + r)−T). The extra needed is MT − M. For the example, finishing 15 years from now (T = 180) takes $2,961.29 a month, or $632.73 extra, saving $165,537.
How much do extra payments save?
Extra monthly payments on the example loan ($329,461 left at 7%, 25 years remaining):
| Extra per month | Paid off in | Time saved | Interest saved |
|---|---|---|---|
| $50 | 23 years 8 months | 1 year 4 months | $23,727 |
| $100 | 22 years 6 months | 2 years 6 months | $44,233 |
| $200 | 20 years 6 months | 4 years 6 months | $78,049 |
| $300 | 18 years 10 months | 6 years 2 months | $104,931 |
| $500 | 16 years 4 months | 8 years 8 months | $145,290 |
| $1,000 | 12 years 5 months | 12 years 7 months | $205,675 |
An extra $200 a month from the first payment of a new 30-year, $300,000 mortgage, by interest rate:
| Rate | Monthly P&I | Interest without extra | Time saved | Interest saved |
|---|---|---|---|---|
| 5% | $1,610.46 | $279,767 | 6 years 5 months | $69,210 |
| 5.5% | $1,703.37 | $313,212 | 6 years 7 months | $79,774 |
| 6% | $1,798.65 | $347,515 | 6 years 9 months | $91,173 |
| 6.5% | $1,896.20 | $382,633 | 6 years 11 months | $103,449 |
| 7% | $1,995.91 | $418,527 | 7 years 1 month | $116,640 |
| 7.5% | $2,097.64 | $455,152 | 7 years 4 months | $130,781 |
| 8% | $2,201.29 | $492,466 | 7 years 6 months | $145,906 |
Biweekly mortgage payments explained
With a biweekly plan you pay half of your monthly payment every two weeks. There are 52 weeks in a year, so that is 26 half-payments, the same as 13 full monthly payments instead of 12. The 13th payment goes to principal each year, which is where the savings come from.
On the example loan, the extra $2,328.56 a year pays the mortgage off 4 years 5 months early and saves $76,255 in interest. The calculator models this as one-twelfth of a payment ($194.05) added every month, which is how the extra money is usually credited when a servicer collects half-payments and applies them as full payments. You can get the same result on your own by adding that amount to each payment, so there is no need to pay a third party to set up a biweekly program. Before switching, confirm how your servicer handles partial payments.
Prepayment penalties
The Consumer Financial Protection Bureau explains that a prepayment penalty is a fee some lenders charge if you pay off all or part of a mortgage early, and that you would have agreed to it at closing. Not all mortgages have one. It typically applies only when you pay off the entire balance, for example by selling or refinancing, within a certain number of years (usually three or five), and sometimes when you pay a large amount at once. It normally does not apply to small extra principal payments. Check your loan documents or ask your lender if you are unsure.
Should you pay off your mortgage early or invest?
There is no single right answer; it depends on your rate, your other finances and how you feel about debt and risk. Points to weigh:
- Guaranteed vs. expected return. Every extra dollar on the mortgage “earns” your interest rate with certainty. Investing may earn more over long periods, but returns are not guaranteed and can be negative for years.
- Liquidity. Money paid into your home is hard to get back without selling or borrowing. An emergency fund usually comes first.
- Other debts and matches. Higher-rate debt, such as credit cards, and any employer retirement match typically offer a better return than prepaying a mortgage.
- Taxes. If you itemize, part of your mortgage interest may be deductible, which lowers the effective rate you save by prepaying. If you take the standard deduction, it doesn’t apply.
- Peace of mind. Owning your home outright lowers your fixed costs in retirement, which matters to many people regardless of the math.
If current rates are well below yours, refinancing may save more than prepaying; compare with the refinance calculator. To price a new home loan, use the mortgage calculator.
Frequently asked questions
How much sooner will I pay off my mortgage with extra payments?
It depends on your balance, rate and how much you add. In our example, $200 extra a month on a $329,461 balance at 7% cuts 4 years 6 months off the remaining 25 years and saves $78,049. Extra payments made early in the loan save the most, because they stop interest from accruing on that money for longer.
Is it better to make extra monthly payments or one lump sum?
For the same total dollars, paying sooner always saves more interest, so a lump sum today beats spreading it over the year. A one-time $10,000 payment on the example loan saves $43,367 and 1 year 10 months. Monthly extras are easier for most budgets; the calculator lets you combine monthly, yearly and one-time payments.
Do biweekly mortgage payments really save money?
Yes, because 26 half-payments a year add up to 13 monthly payments instead of 12. On the example loan that extra payment each year saves $76,255 and 4 years 5 months. You get the same effect by adding one-twelfth of your payment ($194.05) every month, without enrolling in a biweekly program that may charge a fee.
How much extra do I need to pay to pay off my mortgage in 15 years?
On a $329,461 balance at 7%, finishing in 15 years from now takes $632.73 a month on top of the $2,328.56 payment, or $2,961.29 in total, and saves $165,537 in interest. Choose “Target payoff date” in the calculator to find the amount for your own loan and date.
Is there a penalty for paying off a mortgage early?
Only if your loan has one; not all mortgages do. According to the CFPB, a prepayment penalty typically applies only if you pay off the entire balance, for example by selling or refinancing, within a set number of years, usually three or five, and normally does not apply to small extra principal payments. Check your loan documents or ask your lender.
Does paying extra lower my monthly mortgage payment?
Usually not. On a standard fixed-rate mortgage, extra principal shortens the loan, but the required payment stays the same until the loan is paid off. After a large lump-sum payment, some lenders will recast the loan, re-figuring the payment on the lower balance. Ask your servicer whether that is available and what it costs.