Mortgage Recast Calculator
A mortgage recast allows you to make a lump-sum payment toward your mortgage principal balance while your lender re-amortizes the remaining balance over your existing term and interest rate.
Enter Parameters
Adjust inputs to calculate real-time estimates
Showing an initial illustrative scenario using standard parameters. Adjust the input fields on the left and click Calculate now to evaluate your specific numbers.
Calculation Summary
Your recasted monthly payment drops to $1,823.06, saving $337.60 every month.
New monthly payment
$1,823.06
Monthly payment reduction
$337.60
New principal balance
$270,000.00
Lifetime interest saved
$51,031.07
A mortgage recast applies a lump-sum principal payment and re-amortizes your existing balance over the remaining term without altering your interest rate or loan maturity date.
Visual Analytics & Breakdown
Financial Distribution Diagram
Interactive circular proportion of financial allocation
What this mortgage recast calculator is showing you
A mortgage recast allows you to make a lump-sum payment toward your mortgage principal balance while your lender re-amortizes the remaining balance over your existing term and interest rate. Purpose-built for practical decision-making, the Mortgage Recast Calculator provides quantitative clarity on this financial problem by transforming raw input assumptions into structured, actionable projections. Calculations reflect Australian Taxation Office (ATO) Stage 3 personal tax brackets, the 2.0% Medicare Levy, and statutory Superannuation Guarantee rates.
Calculations are performed using the mathematical model New Payment = P_new * r * (1 + r)^n / ((1 + r)^n - 1), where P_new is (Current Balance - Lump Sum) and n is remaining monthly payments.. In this computation, Current loan balance ($) establishes the baseline scale, while parameters such as Annual interest rate (%) determine the progression over time. Adjusting these values allows you to observe how incremental changes directly influence your final outcome.
Mathematical Model
New Payment = P_new * r * (1 + r)^n / ((1 + r)^n - 1), where P_new is (Current Balance - Lump Sum) and n is remaining monthly payments.
Inputs that matter most
Understanding how each variable impacts the final calculation
Current loan balance ($)
Your remaining mortgage principal balance before the recast.
Annual interest rate (%)
Your existing fixed mortgage interest rate.
Remaining loan term (years)
Years left on your current mortgage schedule.
Lump sum principal payment ($)
One-time extra principal payment applied to the loan.
Lender recast administrative fee ($)
Standard fee charged by lenders to re-amortize the loan (typically $150 to $500).
How to interpret your results
Examine the monthly payment breakdown between principal and interest. In early years, interest constitutes the majority of your installment, while principal equity builds progressively over the amortization schedule.
Compare 15-year and 30-year terms to evaluate the trade-off between monthly cash flow affordability and cumulative lifetime interest savings. Confirm that total housing costs remain within conservative debt-to-income benchmarks (typically under 28% of gross monthly income).
- âś“ Verify the Annual Percentage Rate (APR) rather than the nominal interest rate alone, as APR accounts for upfront lender points and origination fees.
- âś“ Test scenarios with additional principal payments to evaluate how accelerated amortization shortens your loan payoff timeline.
- ✓ Budget for auxiliary homeownership expenses—such as property taxes, homeowners insurance, and maintenance—which are separate from principal and interest.
Worked Example Scenario
The snapshot below illustrates a representative calculation using the standard initial parameters:
New monthly payment
$1,823.06
Monthly payment reduction
$337.60
New principal balance
$270,000.00
Lifetime interest saved
$51,031.07
A mortgage recast applies a lump-sum principal payment and re-amortizes your existing balance over the remaining term without altering your interest rate or loan maturity date.
Mortgage Recast Calculator Assumptions & Planning Boundaries
This calculator executes deterministic mathematical models based on New Payment = P_new * r * (1 + r)^n / ((1 + r)^n - 1), where P_new is (Current Balance - Lump Sum) and n is remaining monthly payments.. It assumes that entered parameters—such as Current loan balance ($) and associated rates—remain constant throughout the evaluated period without unmodeled mid-cycle adjustments.
In real-world financial environments, factors including macroeconomic interest rate shifts, localized tax regulations, loan origination fees, closing costs, and inflation variability may cause actual outcomes to differ from theoretical calculations. These figures should be utilized as an analytical planning baseline rather than a legally binding quotation.
Key Factors to Review:
- • Fixed interest rate assumption: Calculations assume the mortgage interest rate remains level over the full term without resets.
- • Escrow exclusions: Standard models exclude property taxes, homeowner insurance, HOA dues, and private mortgage insurance (PMI) unless specified.
- • Prepayment dynamics: Projections assume standard scheduled amortization without factoring in unplanned early principal paydowns.
Frequently Asked Questions
How does a mortgage recast differ from refinancing? â–Ľ
Refinancing replaces your existing loan with a brand-new mortgage, resetting the term and requiring closing costs (typically 2% to 5% of the loan). A recast keeps your existing interest rate, loan term, and note, but recalculates monthly payments downward after a lump-sum principal reduction for a small fee ($150 to $500).
Do all mortgages qualify for recasting? â–Ľ
Most conventional conforming Fannie Mae and Freddie Mac loans allow recasting once minimum lump-sum thresholds (usually $5,000 to $10,000) are met. However, government-backed loans including FHA, VA, and USDA mortgages generally prohibit recasting under statutory guidelines.