How to use this calculator
- Enter current mortgage balance, principal lump-sum payment, nominal annual rate (%), remaining months.
- Choose a display currency, then select Calculate. Results also update after a brief pause while you edit.
- Read the result with the assumptions below. Export details or save a second scenario to compare your choices.
Formula and method
Assumptions and limitations
Lender eligibility and fees are not determined; assumes unchanged rate and term. A normal prepayment does not automatically recast a loan.
Worked example
For the sample inputs shown above, mortgage recast payment produces a first result of approximately 1000. The assumptions below explain what this result represents.
What the result means
Estimate how an eligible principal reduction changes the payment after a formal lender recast.
Common questions
How is the calculation performed?
Recast payment=amortizing payment on (balance−lump sum) over unchanged remaining term and rate.
What does the model leave out?
Lender eligibility and fees are not determined; assumes unchanged rate and term. A normal prepayment does not automatically recast a loan.
Methodology and transparency
Calculation specification reviewed on 2026-10-14. Mathematical implementation is tested against independent reference fixtures. This does not imply review by a licensed financial professional. Read the testing and precision policy.