Calculator Tools
Mortgage Recast Calculator
Calculate the new monthly payment and lifetime interest saved by recasting a mortgage. Compare a recast against prepaying the same lump sum without recasting.
How do you know your current balance
Enter the balance shown on your latest statement together with how many years are left on the loan.
Current loan
The loan you have right now. Enter values exactly as they appear on your most recent mortgage statement.
The rate does not change in a recast. Enter the rate on your existing loan.
Recast
The lump-sum principal payment you plan to make, plus the re-amortization fee your servicer charges.
Most servicers require a minimum (often 5,000 to 10,000) and only allow one recast per loan. Confirm with your lender before sending the payment.
Typical recast fees range from 0 to 500. Much cheaper than refinance closing costs (commonly 2 to 5 percent of the loan).
Result
New monthly payment
$1,823.06
Down from $2,160.66 today; you keep $337.60 in cash flow each month.
Interest saved by recasting
$51,281
Net of the $250 recast fee: $51,031.
Recast vs prepay
$95,063
Recasting costs this much more in lifetime interest than applying the same lump sum without recasting and finishing the loan 91 months sooner.
Current balance
$320,000.00
Outstanding balance as entered.
Current monthly payment (P&I)
$2,160.66
Principal and interest on the loan as it stands today.
Lump-sum recast payment
$50,000
Applied as a one-time principal payment before re-amortization.
Recast fee
$250
Lenders typically charge 0 to 500 to process a recast.
New principal after recast
$270,000.00
Current balance minus the lump sum (recast fee is paid separately).
New monthly payment (P&I)
$1,823.06
Re-amortized over the unchanged remaining term at the same rate.
Monthly payment savings
$337.60
Lower payment every month for the rest of the loan.
Remaining term
25 yr
Unchanged. A recast keeps the original payoff date.
Total interest if you do nothing
$328,199
Sum of interest from today until payoff at the current payment.
Total interest after recast
$276,918
Sum of interest from today until payoff at the new payment.
Interest saved by recasting
$51,281
Lifetime interest reduction from the smaller principal.
Total cost of recasting
$50,250
Lump sum plus the recast fee. The lump sum is principal, not a cost; the fee is the only true cost.
Net interest savings minus fee
$51,031
Lifetime interest savings after subtracting the recast fee.
Prepay without recast: payoff time
17 yr 5 mo
If you applied the same lump sum without recasting and kept paying the current monthly payment.
Prepay without recast: months saved
91 mo
Months shaved off the term compared to doing nothing.
Prepay without recast: total interest
$181,854
Sum of interest from today until payoff if you keep the current payment.
Prepay without recast: interest saved
$146,345
Lifetime interest reduction from prepaying without recasting. Usually larger than the recast number because the borrower keeps paying the same monthly amount.
Recast vs prepay: extra interest under recast
$95,063
Recasting costs more in lifetime interest because the payment drops instead of finishing the loan faster.
All math runs in your browser. Loan balances, rates, and lump-sum amounts never leave your device.
Worked examples
Tap any preset to load realistic numbers and see how the recast math works for that scenario.
How the math works
- Recast formula: new principal = current balance minus the lump sum. The lender then re-amortizes the remaining payments with the same rate and the same remaining term, producing a smaller monthly payment.
- Current balance: when you provide the original loan plus months paid, we use the closed-form remaining-balance formula. When you provide a current balance directly, we use it as-is.
- Lifetime interest: total interest you would still pay at the current payment, minus total interest at the new payment, both summed over the same remaining term.
- Prepay comparison: we apply the same lump sum to principal but hold the monthly payment fixed, then solve for the new payoff date. This usually saves more total interest than a recast because every extra dollar of payment continues attacking the principal.
- Recast fee: charged once by your servicer to re-amortize the loan. It is not added to the new principal; it is paid separately.
What to watch out for
- Recasting is generally available on conventional conforming loans. FHA, VA, USDA, and most jumbo loans typically cannot be recast. Confirm with your servicer before sending the lump sum.
- Lenders usually allow one recast per loan and require a minimum lump sum (commonly 5,000 to 10,000) plus a small fee.
- A recast keeps the original payoff date and lowers the monthly payment. Prepayment without recast keeps the payment the same and shortens the loan. Both reduce total interest; prepay tends to reduce more, recast frees up cash flow.
- Property taxes, homeowners insurance, PMI, and HOA dues are not part of the P&I figures shown here. Use a full mortgage calculator for the complete PITI bill.
- This tool does not provide financial advice. The numbers above are estimates based on the inputs you provide and standard fixed-rate amortization math.
How to use
- Pick how you know your current balance: use the figure from your latest statement or derive it from the original loan, term, rate, and months paid.
- Enter your interest rate. The rate does not change in a recast, so use the rate on your existing loan.
- Enter the lump-sum amount you plan to apply and the recast fee your servicer charges (often 0 to 500).
- Read the new monthly payment, the lifetime interest saved by recasting, and the side-by-side recast vs prepay comparison.
- Tap any preset to load a realistic scenario, or use Copy summary to capture the full result for a follow-up call with your lender.
About this tool
Mortgage Recast Calculator shows what happens when you apply a lump-sum principal payment to your mortgage and ask the lender to re-amortize. A recast keeps your interest rate and your payoff date unchanged, but the smaller principal produces a smaller monthly payment and reduces total interest. Enter your current balance (or derive it from the original loan, rate, term, and months paid), your rate, and the lump-sum amount you plan to send. The tool computes the new monthly payment, the lifetime interest you would save versus doing nothing, and the net savings after the recast fee your servicer charges. A built-in comparison shows what the same lump sum would do if you simply applied it as a one-time extra principal payment without recasting: the monthly payment stays the same and the loan finishes earlier. That path usually saves more lifetime interest, while a recast frees up monthly cash flow. Recasting is generally available on conventional conforming loans (FHA, VA, USDA, and most jumbo loans typically cannot be recast), usually requires a minimum lump sum of 5,000 to 10,000, costs a small fee (often 0 to 500), and is allowed once per loan. All math runs in your browser. Loan balances, rates, and lump-sum amounts never leave your device.
Free to use. Works in your browser. No signup, no login.
Related tools
You may also like
Mortgage Calculator
Full PITI mortgage payment with PMI, HOA, extra principal, and amortization schedule.
Open tool
CalculatorMortgage Refinance Calculator
Monthly savings, break-even point, lifetime interest, and APR for any refinance offer.
Open tool
CalculatorAmortization Schedule Generator
Full amortization schedule with extras, lump sum, and bi-weekly comparison.
Open tool
CalculatorMortgage Points Calculator
Break-even months, monthly savings, and lifetime cost for any mortgage point buy-down.
Open tool
CalculatorLoan Calculator
Monthly payment, total interest, payoff time, and amortization schedule.
Open tool
CalculatorDebt Payoff Calculator
Snowball or avalanche payoff with side-by-side comparison and monthly schedule.
Open tool