Mortgage recast calculator
Compare a lump-sum mortgage recast with the same principal payment applied without a recast. Enter the balance, current rate, remaining term, lump sum, and any servicer fee from your own records.
What drives the calculator result
The model uses the entered unpaid balance, interest rate, remaining term, lump sum, and servicer fee. It recalculates a principal-and-interest payment from those inputs; it does not read the mortgage statement or determine whether the loan is eligible.
Use the separate mortgage recast guide linked below for eligibility, servicing process, timing, fees, and decision tradeoffs. Confirm every account-specific figure and instruction directly with the servicer before sending money or relying on a new payment.
Recast versus principal prepayment
The same lump sum can produce two different modeled cash-flow paths. With a recast, the estimated required principal-and-interest payment drops while the modeled payoff date stays the same. Without a recast, the tool assumes the servicer applies the lump sum to principal and the borrower continues the prior modeled payment, which can pay the balance off earlier.
This calculator shows both paths because the better choice depends on the goal: lower required monthly cash flow, earlier payoff, liquidity, or the cost and eligibility of the servicer's recast process.
What the estimate leaves out
- Servicer-specific eligibility, timing, minimum principal payments, and fees.
- Escrow changes, mortgage insurance, late charges, payment history, or pending servicing activity.
- Any effect of daily interest, unusual payment schedules, adjustable rates, or loan modifications.
- Tax, investment-return, emergency-reserve, and opportunity-cost considerations.
For servicing guidance, start with your own servicer. Fannie Mae's servicing guide also explains a servicer's responsibilities when re-amortizing an eligible loan after a substantial principal curtailment.
Mortgage recast calculator questions
What figures does the mortgage recast calculator need?
Enter the current unpaid balance, interest rate in effect, remaining term, planned principal payment, and any fee quoted by the servicer. Use figures from the current statement or servicer rather than estimates when possible.
Why is the current principal-and-interest payment estimated?
The calculator derives principal and interest from the entered balance, rate, and remaining term. A servicer's amount can differ because of payment timing, daily interest, prior curtailments, adjustable-rate provisions, modifications, rounding, or other account details.
What does the fee comparison mean?
It shows how many months of the modeled principal-and-interest reduction equal the entered fee. It does not evaluate the lump sum, liquidity, taxes, investment returns, or opportunity cost, so it is not a full break-even analysis.
Does the calculator include taxes, insurance, or mortgage insurance?
No. It models principal and interest only. Property taxes, homeowners insurance, mortgage insurance, and other escrow items are separate and can change independently.
Why can a servicer's recast quote differ from the calculator?
The servicer uses the actual account balance, payment application, effective date, note provisions, investor requirements, fees, and internal rounding. The calculator uses only the figures entered and is an educational estimate.
What does the principal-payment-without-recast path assume?
It assumes the entered lump sum is applied to principal and the prior modeled principal-and-interest payment continues. That can shorten payoff, but the servicer's application of funds, the note, any prepayment penalty, and the actual payment history control.
Comparing a recast with a refinance?
Send me the current balance, rate, remaining term, and what you want the loan to accomplish. I will help you compare the mortgage math while your servicer remains the authority on recast eligibility.