Mortgage recast calculator
One lump sum. Three perspectives. Compare keeping your current loan, recasting after a principal payment, and making the same payment without recasting.
Your current mortgage
Change the numbers to explore your scenario.
25 yr remaining
Applied to your balance before the next payment.
Paid separately; not added to the loan.
Example inputs are illustrative and are not a rate quote.
Monthly principal & interest
$1,823.06 to the nearest cent
Your balance over time
- Balance after lump sum
- $270,000
- Total interest
- $276,918
- Time to pay off
- 25 yr
Three ways to move forward
| Scenario | Monthly P&I | Total interest | Payoff time |
|---|---|---|---|
| Keep current loan | $2,160.66 | $328,199 | 25 yr |
| Lump sum + recast | $1,823.06 | $276,918 | 25 yr |
| Lump sum only | $2,160.66 | $181,855 | 17 yr 6 mo |
Both lump-sum scenarios start with a $50,000 principal payment. The recast scenario also includes a separate $250 fee. Compare the cash you use upfront as well as future savings.
Estimates assume a fixed interest rate, monthly payments, and extra payments applied directly to principal. Recasting availability, minimum payments, and fees depend on your loan servicer. Lender rounding, payment dates, fees, and loan terms can change your actual costs. This is a planning estimate, not a loan offer.
Compare the same lump sum
Enter your current principal balance, interest rate, and remaining term. Add the lump sum you want to explore and a recast fee. The calculator keeps the interest rate the same across all three scenarios, making it easier to compare payment amounts and timelines.
How the estimate works
For a fixed-rate loan, the monthly principal and interest payment is calculated using:
M = P × r / (1 − (1 + r)−n)P is the starting balance, r is the annual interest rate divided by 12 (as a decimal), and n is the number of monthly payments. At 0% interest, the payment is the balance divided by the number of months.
Assumptions to keep in mind
The lump sum is applied immediately, before the next month’s interest. The recast fee is paid separately and deducted from displayed net interest savings; it is not financed. Taxes and insurance are excluded. Servicer eligibility, minimum amounts, processing times, and fees are not modeled.
Calculations retain full precision internally; displayed amounts and CSV values are rounded to cents. Your servicer’s rounding and payment timing can produce small differences.
Fannie Mae: Recast loan overviewGood questions to ask
What does the recast scenario change?
It reduces the balance by your lump-sum payment, then recalculates principal and interest over the remaining term. The entered interest rate stays the same. Availability and terms must be confirmed with your servicer.
What happens in the lump-sum-only scenario?
This scenario applies the same principal reduction but keeps the original monthly principal and interest payment. In the model, the lower balance is then paid off sooner than it would be with the smaller recast payment.
Is a recast the same as refinancing?
This calculator models re-amortizing an existing balance at its existing rate. It does not model replacing a mortgage with a new loan, changing the rate, or paying refinance closing costs.
Can I use this as a recast approval?
No. Ask your loan servicer whether your mortgage is eligible and confirm its required payment, fees, and effective date. The calculated savings do not account for what you could otherwise do with the lump sum.