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Mortgage Recast Calculator
Put a lump sum toward your mortgage and see the lower payment a recast gives you, versus keeping your payment and finishing early.
Assumes an eligible fixed-rate loan. Both the old and new payments are derived from the entered balances and remaining term and rounded upward to a cent. The fee is paid upfront. Escrow, penalties and lender-specific rounding or posting rules are excluded.
| Principal remaining after the lump sum | $300,000.00 |
| Interest saved by recasting (after fee) | $51,029.39 |
| If you prepay and keep the old payment: paid off in | 18 years 8 months |
| Interest remaining if you prepay instead | $208,974.66 |
| Extra interest and fee vs prepaying | $98,933.00 |
How a recast is calculated
new balance = balance − lump sum new payment = new balance × r ÷ (1 − (1 + r)^−months remaining), r = rate ÷ 12 net interest savings = baseline interest − recast interest − fee
Years convert to the nearest whole month. The prepay comparison keeps the modeled old payment on the reduced balance; recasting recalculates a lower payment over the remaining term. Each monthly schedule uses an adjusted final payment and retains interest precision until display. Escrow is excluded.
Frequently asked questions
What does a mortgage recast do?
If your servicer permits it, a principal reduction can be followed by recalculating principal-and-interest payments using the reduced balance, current rate and remaining term. The calculator assumes that kind of recast; it does not determine eligibility.
How does recasting compare with keeping the payment unchanged?
The comparison applies the same lump sum in both cases. Keeping the modeled old payment retires principal faster when the rate is positive. At the defaults, that alternative finishes in 18 years 8 months; recasting instead lowers the payment.
Is the monthly payment reduction a profit or investment return?
No. It is a cash-flow change. Compare the recast fee and total interest as well as the payment; a smaller required payment can leave the debt outstanding longer than keeping the higher payment.
Can every mortgage be recast?
Eligibility, required principal reduction, fees and approval procedures depend on your loan and servicer. Ask for the applicable policy before relying on this scenario. The calculator does not assume a universal minimum lump sum or fee.
What if the lump sum pays off the entire balance?
That is a payoff rather than a recast. Use the mortgage payoff calculator. This recast model requires some principal to remain after the lump sum.
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Sources and updates
Methods and figures reviewed on . Provider rates and terms can change; check the linked source and your own account terms.
This calculator gives estimates for information only and is not tax, legal or financial advice. Actual outcomes depend on the assumptions, timing, taxes, fees and terms that apply to you. See how we calculate.