Mortgage Recast Calculator
Estimate how a lump-sum principal payment could lower your required principal-and-interest payment when the same rate and remaining term are retained.
Estimate a recast
Modeled current P&I—
Balance after lump sum—
Monthly payment reduction—
Remaining interest reduction—
Fee / payment-reduction break-even—
A recast typically keeps the current rate and remaining payoff date while re-amortizing a lower principal balance. Eligibility and fees vary by servicer and loan type.
Recast versus extra principal
A recast lowers the required payment after the lump sum. Simply making the same principal payment without recasting generally leaves the required payment unchanged and can shorten payoff time instead.
Method references
Rocket Mortgage, Chase, NerdWallet and Bankrate all describe recasting as re-amortizing the reduced balance at the existing rate over the remaining term. Reviewed September 30, 2026.