Mortgage Recast Calculator
Estimate a new monthly principal-and-interest payment after a lump-sum principal reduction, including interest savings, the recast fee, and fee break-even time.
Maintained by Archie Chang · Data and formulas checked September 3, 2026 · Methodology & sources
Current Loan and Proposed Recast
Use the unpaid principal balance and remaining term from your latest statement. Enter only the principal curtailment—not the recast fee—in the lump-sum field.
What the Estimate Includes
This tool models the voluntary mortgage re-amortization described by Fannie Mae after a substantial principal curtailment: the new unpaid balance is amortized at the existing rate over the existing remaining term. It compares the scheduled principal and interest before and after that change.
It does not model escrow, mortgage insurance, a changed interest rate, a changed maturity date, taxes, investment returns, or loan-specific qualification rules. A servicer's quote controls the actual contractual payment.
Estimated New Payment
$1,688.02
Monthly principal and interest
- Current P&I payment
- $2,025.62
- Monthly savings
- $337.60
- New principal balance
- $250,000
- Remaining interest saved
- $51,281
- Net savings after fee
- $51,031
- Fee-only cash-flow break-even
- 1 month
Mortgage Recast vs. Extra Principal vs. Refinance
| Option | Required payment | Rate and term | Typical tradeoff |
|---|---|---|---|
| Recast | Recalculated lower after approval | Existing rate and remaining term | Uses a lump sum; may require a fee and eligibility review |
| Extra principal only | Usually unchanged | Existing rate; earlier payoff if payments continue | Saves interest but does not normally lower the amount due |
| Refinance | Set by a new loan | May change both | New underwriting and potentially substantial closing costs |
Mortgage Recast Questions
What is a mortgage recast?
A mortgage recast, also called re-amortization after a principal curtailment, recalculates the required monthly principal-and-interest payment after you make a substantial lump-sum principal payment. The remaining balance is spread over the remaining term at the existing interest rate. Your servicer must approve and process it.
How is a recast mortgage payment calculated?
The new payment uses the standard fixed-payment amortization formula with three inputs: the balance after the lump-sum payment, the existing interest rate, and the number of monthly payments remaining. This calculator does not extend the term or substitute a new interest rate.
Does a mortgage recast change the interest rate or loan term?
Normally, no. A recast lowers the unpaid principal balance and recalculates principal and interest over the remaining term using the current note rate. It is different from refinancing, which replaces the loan and may change the rate, term, and closing costs.
Can every mortgage be recast?
No. Eligibility, minimum principal curtailment, fees, seasoning requirements, and processing rules depend on the loan, investor, and servicer. Ask your mortgage servicer for written eligibility and a formal payment quote before sending a lump sum.
Does the new payment include property tax and insurance?
No. This calculator compares principal and interest only. Escrowed property taxes, homeowners insurance, mortgage insurance, HOA dues, and other charges can keep the total amount due higher and may change independently.
Is a mortgage recast the same as making an extra principal payment?
No. An extra principal payment reduces balance and interest, but the required monthly payment normally stays the same unless the servicer completes a recast. Keeping the old payment after a principal reduction can pay the loan off earlier; recasting instead lowers the required payment over the original remaining term.
When can a mortgage recast be worth considering?
A recast may be useful when you want a lower required payment without replacing a favorable mortgage rate. Compare the payment reduction, interest savings, servicer fee, cash you would give up, and alternative uses for that cash. The calculator is an estimate, not a servicer quote or recommendation.
Related calculators
Authoritative sources: Fannie Mae recast loan overview · Fannie Mae additional principal payment guide · CFPB mortgage resources