Mortgage Payoff Calculator
Mortgage & Extra Payments
Savings Summary
| Normal Monthly Payment | — |
|---|---|
| Accelerated Payoff Term | — |
| Time Saved | — |
| Total Interest Saved | — |
| Total Interest (Original) | — |
| Total Interest (New) | — |
Visual Breakdown
Enter values and press Calculate to see the loan breakdown pie chart and balance path line chart.
How to Use This Mortgage Payoff Calculator
Sending an extra $100 with your mortgage payment feels small, but over years it can cut tens of thousands in interest. The hard part is seeing exactly how many months that buys you. Plug in your current balance, rate, and any extra payment plan here—monthly, annual, or a one-time lump sum—and the accelerated schedule shows the payoff date and interest saved.
- Enter current loan balance, rate, and remaining term. Use the payoff amount from your servicer, not the original purchase price.
- Add optional extra payments. Set a recurring monthly extra, an annual lump sum (with the month it applies), or a one-time payment in a specific month.
- Press Calculate. Review normal payment, new payoff term, time saved, interest saved, charts, and the accelerated schedule.
For the base payment without extras, use the Mortgage Calculator. To compare refinancing instead of prepaying, try the Refinance Calculator.
Mortgage Payoff Formulas and Practical Applications
Extra payments work like chipping away at the bottom of a stack—the next month's interest is calculated on whatever is left, so every dollar of principal you remove today stops generating interest forever. That compounding effect is why even modest extras beat waiting.
Standard month split
Interest_t = Balance_{t−1} × i
Principal_t = M − Interest_t
Applying extras to principal
Extras stack on top of the scheduled principal portion, capped so you cannot pay more than the remaining balance:
Total Principal_t = min(Principal_t + Extra_t, Balance_{t−1})
Balance_t = Balance_{t−1} − Total Principal_t
On a $300,000 balance at 6% with 30 years remaining, adding $100 per month can save roughly $45,000 in interest and finish the loan about 4 years early—exact figures appear in your results table.
Frequently Asked Questions
Do extra mortgage payments go to principal?
This calculator assumes extra amounts are applied directly to principal after the scheduled P&I split. Confirm with your servicer that payments are coded correctly—some require a written instruction.
How much can an extra $100 per month save?
Savings depend on loan balance, rate, and remaining term. On a $300,000 balance at 6% with 30 years left, $100 extra monthly can save tens of thousands in interest and shave several years off the term.
Can I model a one-time lump sum payment?
Yes. Enter a one-time extra payment amount and the month number when it will be applied, such as month 1 for an immediate lump sum after closing.
Are there prepayment penalties?
Some loans charge a fee for paying off early or making large extra payments. This tool does not model penalties—check your note before accelerating payoff.
Should I pay off my mortgage early or invest?
That depends on your mortgage rate, tax situation, and expected investment returns. This calculator shows interest savings from extra payments—it does not compare against investing the same cash.