Mortgage Recast Savings Calculator

A recast saves you two things: a lower monthly payment and the interest on the lump sum for the rest of the loan. On a $300,000 loan at 4.5% with 25 years left, a $50,000 lump sum takes the payment from $1,667.50 to $1,389.58 and cuts the interest left from $200,249 to $166,874.

The table shows the saving for four lump sums. The calculator below does your own loan.

Savings by lump sum

The loan is $300,000 at 4.5% with 25 years left, a payment of $1,667.50 (principal and interest). The fee of $250 is an example, not a quote.

Lump sumNew paymentSaved a monthInterest leftInterest savedNet of $250 feeMonths to cover fee
$10,000$1,611.91$55.58$193,574$6,675$6,4255
$25,000$1,528.54$138.96$183,562$16,687$16,4372
$50,000$1,389.58$277.92$166,874$33,375$33,1251
$100,000$1,111.66$555.83$133,499$66,750$66,5001

Interest left with no lump sum: $200,249. Interest saved = that figure minus the interest left after the recast. The rate and the end date do not change.

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How to read the savings

  1. Monthly saving: the old payment minus the new one. It is cash you keep every month.
  2. Interest saved: what you do not pay the lender over the rest of the loan. This is the real saving.
  3. Net saving: interest saved minus the fee.
  4. Months to cover the fee: fee divided by the monthly saving, rounded up.

A recast saves less interest than paying the same lump sum and keeping your old payment. Chase says a recast reduces or eliminates the interest savings gained from making extra principal payments. The two paths side by side are in recast vs extra principal payment.

Lender savings tools

Chase's recast page links to a savings calculator in Chase MyHome. Your servicer can also tell you the exact fee and the new payment. For the payment formula behind every figure here, see how to calculate a recast payment, and for the fee, how much a recast costs.

Frequently asked questions

How much interest does a recast save?

It saves the interest on the lump sum for the rest of the loan, because the balance is smaller from day one. On the example loan, $50,000 cuts the interest left from $200,249 to $166,874, a saving of $33,375.

Is the interest saved the same as the monthly saving times the months?

Yes, for a recast with no change in rate or end date. $277.92 a month for 300 months is $83,375, the same as the interest saved plus the $50,000 you paid in.

Why does the monthly saving look bigger than the interest saved?

The monthly saving also includes the principal you no longer have to repay. Only the part that was interest counts as a saving. The rest is your own lump sum coming back to you in smaller payments.

Does the fee change the result?

Subtract it from the interest saved. A $250 fee leaves $33,125 on the $50,000 example. Fees vary by lender, so ask for yours in writing.

Would keeping my old payment save more?

Yes. If you pay the lump sum and keep the old payment, the loan ends sooner and the interest left is lower. A recast trades some of that saving for a smaller required payment. See recast vs extra principal payment.

Sources

Every figure on this page comes from the pages below. Checked 2026-10-22. Rules change, so confirm with your own servicer.

More recast guides