Mortgage Recast Calculator
Last updated: October 15, 2026
Estimate a new monthly payment after applying a lump-sum principal reduction.
Estimated new monthly payment
—
- Payment before recast: —
- Monthly savings: —
- New balance: —
- Fee break-even: —
On this page
Quick summary: Estimate a new monthly payment after applying a lump-sum principal reduction.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Estimate a new monthly payment after applying a lump-sum principal reduction.
How to use it
Enter Current balance ($); Lump-sum principal payment ($); Interest rate (%); Remaining term (years); Recast fee ($). Select Calculate to update the results.
How the calculation works
Subtract the lump-sum principal payment from the current balance. Calculate old and new payments using the same interest rate and remaining term. Monthly reduction = old payment minus new payment. Fee-recovery months round the recast fee divided by that monthly reduction upward to a whole month.
Worked example: starting scenario
| Current balance ($) | 320000 |
|---|---|
| Lump-sum principal payment ($) | 50000 |
| Interest rate (%) | 5.75 |
| Remaining term (years) | 24 |
| Recast fee ($) | 300 |
| Estimated new monthly payment | $1,730.56 |
|---|---|
| Payment before recast | $2,051.03 |
| Monthly savings | $320.47 |
| New balance | $270,000.00 |
| Fee break-even | 1 months |
Important limitations
The fee-recovery measure covers the recast fee only. It does not recover or value the lump-sum principal payment, and it excludes the opportunity cost of that cash. The recast fee is assumed paid separately, and lender availability, eligibility, minimum principal payments and escrow changes are not determined here.