Extra mortgage payment calculator
Every dollar you send above the required payment goes straight at the principal, and the interest that principal would have earned for the rest of the loan disappears with it. Enter your loan to see the new payoff date, the months you cut off and the interest you keep.
Your loan
What it saves
| Payoff with no extra payments | 28 yr 4 mo · January 2055 |
| Interest with no extra payments | $451,521 |
| Interest with extra | $355,525 |
| Total interest saved | $95,996 |
Adding $200 a month to principal clears the loan 5 yr 2 mo earlier — around November 2049 instead of January 2055 — and keeps $95,996 of interest in your pocket.
How extra payments are calculated
Each month your lender charges interest on the balance you owe that month. Whatever is left of your payment reduces the balance, so next month's interest is charged on a smaller number. An extra payment skips straight to that second step: the full amount comes off the balance, and every future month's interest is calculated on the lower figure. That is why a modest amount applied early does far more than the same amount applied in year twenty.
Monthly, biweekly, or one lump sum?
A biweekly schedule means 26 half-payments a year, which is one extra full payment annually — this calculator models that as your payment divided by twelve added to principal each month. A fixed monthly amount is easier to control and does the same work. A lump sum from a bonus or a sale is the strongest single move if it lands early in the loan. What matters more than the shape is that the money is applied to principal: write it on the payment or use your servicer's principal-only option, or it may just sit as a prepaid regular payment.
Before you prepay, check three things
- Higher-rate debt first — a 6% mortgage is rarely the most expensive balance you carry.
- Mortgage insurance — if you still pay PMI, extra principal may end it sooner, which is a saving on top of the interest.
- Your payment doesn't drop — prepaying shortens the loan, it does not lower the monthly amount due. A recast does that instead.