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Mortgage Recast Calculator

Apply a lump sum to your principal and re-amortize to a lower monthly payment while keeping your rate and payoff date. See the new payment and interest saved.

Rate fields default to the current 30-year fixed average of 6.35% (as of August 28, 2026, Federal Reserve Economic Data (FRED), St. Louis Fed). Override any field with your own numbers.

New monthly payment
$1,679.63
Down $258.40 / month
Old payment
$1,938.03
Balance after lump sum
$260,000
Lifetime interest saved
$43,723
Break-even on fee
1 month

A recast keeps your rate and payoff date but lowers the payment. Compare with simply making the same lump-sum payment and keeping the higher payment — that saves more interest overall, but a recast improves monthly cash flow.

When a recast makes sense

How it works

  1. You make a lump-sum principal payment (lenders often require a $5,000–$10,000 minimum).
  2. The servicer re-amortizes the reduced balance over your remaining term at your existing rate.
  3. Your payoff date stays the same; your monthly payment drops.

This calculator shows the new payment, the monthly savings, your balance after the lump sum, and — for comparison — the lifetime interest you’d save.

The trade-off, in numbers

Say you owe $300,000 at 6.5% with 27 years left and pay $40,000 down:

Recast if cash-flow flexibility matters to you; keep the higher payment if minimizing total interest is the only goal.

Practical notes

Frequently asked questions

What is a mortgage recast?+

You pay a large lump sum toward principal, and the lender recalculates (re-amortizes) your payment over the same remaining term at the same interest rate. The result is a lower required monthly payment for the rest of the loan.

Recast vs. refinance — which should I pick?+

Recast keeps your existing rate, has a small flat fee (usually $150–$500), and needs no credit check or appraisal. Refinance can change your rate and term but has full closing costs. If your current rate is good and you just want a lower payment after a windfall, recast.

Does a recast save more interest than just prepaying?+

No. Making the same lump-sum payment and keeping your original higher payment saves the most interest, because more goes to principal each month afterward. A recast trades some of that interest savings for improved monthly cash flow.

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