Mortgage Payoff Calculator
See how much interest you save and how much sooner you finish your mortgage by adding extra principal payments — one-time, monthly or annual.
How to use the Mortgage Payoff Calculator
- Enter your inputs into the Mortgage Payoff Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The mortgage payoff mechanics
Each extra payment reduces principal and all future interest is recomputed on the new balance.
There is no closed-form formula because each extra payment compounds the savings on every payment that follows. The calculator simulates the new amortization schedule with the extra payments applied.
Worked example
On a $300,000 mortgage at 6.5% for 30 years, adding $200/month extra cuts the loan by about 7 years and saves roughly $109,000 in total interest. A single $20,000 lump sum in year 5 saves about $63,000.
Frequently asked questions
Should I pay extra or invest instead?
Compare your mortgage rate to your expected after-tax investment return. If your rate is 6.5% and you expect 7% after taxes in the market, the answer is debatable — invest is the higher-EV bet but mortgage prepayment is risk-free.
Are there prepayment penalties?
Federal regulations effectively ended prepayment penalties on most conforming residential mortgages after 2014. Check your loan docs to confirm.
How should I send extra payments?
Specify that the extra amount is applied to principal. Otherwise some servicers credit it as a prepayment toward future scheduled payments instead of reducing the balance.