Tool Factory

Mortgage Recast Calculator

Apply a lump-sum principal payment, keep the remaining term, and see the new monthly payment, payment drop, and interest savings.

  • Lump-sum recast
  • Same remaining term
  • Not a refinance
Remaining term
Recast keeps this remaining term and lowers the monthly payment.

Numbers stay on this device. Nothing is uploaded, and there is no account.

A mortgage recast calculator answers a practical question: if you put a lump sum toward principal, how much does the monthly payment fall when the lender re-amortizes the loan? Recast — sometimes searched as a recast mortgage calculator — keeps the same remaining term and the same rate. Only the balance and the payment change.

That is different from sending extra principal without asking for a recast, which pays the loan off sooner while the payment stays put. It is also different from a refinance, which replaces the loan and can change the rate, term, and closing costs. This tool models the lump-sum recast only.

Enter remaining balance, annual interest rate, remaining years and months, and the principal payment. The page shows the current payment, the new payment after recast, the drop, and interest you avoid versus continuing on the original schedule. Everything runs in your browser. Totals never leave the device, and there is no account.

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How to use the mortgage recast calculator

  1. Enter the remaining loan balance (current principal, not the original amount).
  2. Enter the annual interest rate on the existing loan.
  3. Set the remaining term in years and extra months.
  4. Enter the lump-sum amount you would apply to principal.
  5. Read the new monthly payment, payment drop, and interest savings.

Frequently asked questions

How does a mortgage recast calculator work?

A mortgage recast calculator subtracts your lump-sum principal payment from the remaining loan balance, then re-amortizes that new balance over the same remaining term at the same interest rate. The result is a lower monthly payment — not a shorter loan and not a new rate.

What is the difference between a recast and a refinance?

A recast keeps your existing loan, interest rate, and remaining term, then lowers the payment after a principal reduction. A refinance replaces the loan, can change the rate and term, and usually adds closing costs. This page is a recast mortgage calculator only — it does not model a refinance.

Does a mortgage recast shorten the remaining term?

No. A lump-sum recast keeps the original remaining term and recalculates the payment so the new, lower balance is paid off on the same schedule. Extra principal without a recast would instead shorten the term while the payment stayed the same.

How do you calculate interest savings after a recast?

Interest left without a recast is the current payment times remaining months, minus today’s balance. Interest left after recast is the new payment times the same months, minus the reduced balance. The difference is interest you avoid by paying principal up front.

What lump sum do I need for a recast?

Lenders set their own minimums — often several thousand dollars — and may charge a recast fee. Enter the principal amount you would actually apply. This calculator does not include lender fees or approval rules.

Does this mortgage recast calculator upload my loan numbers?

No. Balance, rate, remaining term, and the lump sum are calculated in your browser. Nothing is sent to a server or stored on our side.

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