Mortgage Payoff Calculator
Monthly extra, a biweekly half-payment, and a lump sum. The columns do not add together. The chart does.
Key concepts
Amortization
The process of paying off a loan through scheduled payments that cover both interest and principal over the loan term.
Extra principal payment
Any amount paid above your required monthly payment that goes directly toward reducing the loan balance, saving interest over time.
What this tool does
What is included
This calculator models principal and interest only. Property taxes, insurance, HOA fees, and PMI are not included. Extra payments go to principal after interest, on the frequency you choose.
How extra payments help
Because interest is charged on the remaining balance, every extra dollar of principal reduces future interest. Compare a monthly extra, half the scheduled payment every two weeks, and a lump sum on a date. Those columns do not add together. The chart does. If you know the payment and not the term, say so and the page solves the month count. This page stays on paying the loan down. It does not compare a refinance.
Amortization payment formula
M = P × [r(1+r)^n] / [(1+r)^n − 1] where r = annual rate / 12, n = term in months
Each month we charge interest on the remaining balance, apply the scheduled payment, then apply any extra amount to principal. We stop when the balance is paid off.
Worked example
The page opens on $350,000 at 6.5% for 30 years, with $300 extra each month and a $10,000 lump sum. The scheduled payment is about $2,212. The monthly column, the lump-sum column, and the biweekly column each use one of those levers. They do not add together. The chart adds the $300 and the $10,000: payoff in month 245, about $172,163 of interest saved.
Common mistakes
- Comparing only monthly payment size and ignoring total interest over the life of the loan.
- Assuming escrow (taxes/insurance) is reduced when you pay principal early — usually it is not.
- Not confirming with the lender that extras apply to principal and that there is no prepayment penalty.
Methodology on this page
Standard fixed-rate amortization for principal and interest only. A monthly extra applies after each month’s interest. Every two weeks pays half the scheduled payment every two weeks, which is 13 full payments a year. It does not multiply an extra amount by 26. Once a year applies the extra in month 12, 24, and so on. A lump sum reduces principal on the date you set, or before the next interest charge if the date is blank, and does not change the scheduled payment. If you know the payment and not the term, the month count is solved from that payment. PMMS 30-year can fill the rate from the Freddie Mac survey and shows the survey date. The field stays editable. Taxes, insurance, HOA, and PMI are excluded. This is not a refinance comparison.
Read the full FinTools4U methodology →Frequently asked questions
How are extra payments applied?
A monthly extra goes to principal after that month’s interest. Every two weeks means half the scheduled payment every two weeks, 13 full payments a year, not the extra amount times 26. Once a year applies the extra in month 12 of each year. A lump sum comes off the balance on the date you pick, or immediately if you leave the date blank, and does not change the scheduled payment.
Does this include taxes or insurance?
No. This calculator focuses on principal and interest only.
Will my lender accept extra payments?
Most lenders allow extra principal payments, but policies vary. Confirm with your lender that extras apply to principal and do not trigger prepayment penalties.
Can I share an extra-payment plan?
Yes. The link keeps the extra amount and the frequency: monthly, every two weeks, or once a year. Extras apply to principal. PMMS 30-year can fill the rate from the Freddie Mac survey and shows the survey date. The field stays editable. This page does not compare a refinance.
Sources & further reading
- CFPB — How to pay off your mortgage early — Consumer guidance on early payoff considerations.
- CFPB — Owning a Home — Educational resources on mortgages and closing.
Related guide
How extra mortgage payments change the payoff
The fixed-rate payoff formula, what an extra principal payment does to interest and term, and how to read the FinTools4U mortgage payoff calculator.
When you can ask to cancel PMI
The month the balance reaches 80% of the original value, the automatic month at 78% on the schedule with no extra, and why extra principal moves only the request.
Related calculators
Mortgage Payment Calculator
Principal and interest, plus optional taxes, insurance, and PMI.
Amortization Schedule
Month-by-month principal, interest, and remaining balance.
Debt Snowball vs Avalanche
Have multiple debts? Compare payoff strategies side by side.
Refinance Break-even
A different question, about replacing the loan rather than paying this one down.