Immediate principal reduction
The entered lump sum is subtracted from the current mortgage balance before the next modeled interest charge.
Mortgage Payoff with Lump Sum Calculator
See how a one-time principal payment and optional extra monthly payments can change your mortgage payoff.
Your inputs
Calculation details
⌁ All calculations run locally in your browser. No data is stored.
Time saved10 yr 2 mo
Interest saved$163,750.26
New payoff time19 yr 10 mo
Regular monthly payment$1,896.20
The lump sum is applied immediately to principal. The regular payment is estimated from the current balance, rate, and remaining term; lender posting rules can differ.
Compare payoff strategies
How a lump sum changes mortgage payoff
A one-time mortgage payment reduces the balance on which future interest is charged. The benefit depends on the payment amount, interest rate, time remaining, and whether the lender applies the money directly to principal.
Scheduled payment stays the same
The estimate assumes the regular principal-and-interest payment continues unchanged unless your lender completes a loan recast.
Interest and time comparison
The original amortization schedule is compared with the accelerated schedule to estimate interest saved and months removed.
Lump sum vs. extra principal payments
A lump sum is useful for modeling a bonus, inheritance, asset sale, or other one-time amount. An extra principal payment models a smaller amount paid repeatedly with the monthly mortgage payment.
Use the Extra Mortgage Payment Calculator when you only want to test a recurring payment. Use this calculator when the timing and size of a one-time payment matter.
Before sending a large payment
Confirm that your servicer will apply the amount to principal and whether your loan has a prepayment penalty. Ask whether a recast is available if your goal is a lower required payment rather than an earlier payoff.
This estimate excludes taxes, insurance, escrow changes, lender fees, and investment returns you might earn by keeping the cash.
This calculator models a fixed-rate amortizing mortgage and assumes payments are posted as entered. Your lender’s posting date, recast rules, fees, and prepayment terms can change the actual result.
How this calculator works
The calculator estimates the scheduled payment for the remaining balance and term, then compares that schedule with one where the lump sum is applied immediately to principal and any recurring extra amount is added each month.
Change any input to update the estimate instantly. Your entries never leave your device.
Read how SimpleCalc defines formulas, assumptions, and accuracy checks.
Frequently asked questions
Does a lump-sum payment lower my required monthly payment?
Usually not unless your lender formally recasts the loan. This estimate keeps the scheduled monthly payment unchanged and shortens the payoff schedule.
Are prepayment penalties included?
No. Check your loan documents and lender policy before making a large principal payment.
When is the lump sum applied?
It is modeled as an immediate principal reduction before the next monthly interest charge.
What is the difference between a lump sum and an extra monthly payment?
A lump sum reduces principal once. An extra monthly payment adds a recurring principal amount to every scheduled payment.
Can I combine a lump sum with extra monthly principal?
Yes. Enter both amounts to estimate their combined effect on payoff time and interest.