Mortgage Recast Calculator

Spluxly’s free online Mortgage Recast Calculator is a comprehensive home loan optimisation tool designed for homeowners who want to reduce their monthly mortgage payment by making a lump sum payment toward their principal without the cost and complexity of refinancing. A mortgage recast — also known as a loan re-amortisation — involves paying a significant lump sum directly against the outstanding principal balance, after which the lender recalculates the monthly payment based on the new lower balance while keeping the original interest rate and remaining loan term unchanged. Enter your original loan amount, current principal balance, annual interest rate, original loan term, time remaining on the loan, and the lump sum amount you plan to apply, and the calculator instantly delivers a full comparison between your current mortgage and the recast scenario. Results include the new monthly payment, monthly savings in dollars and percentage, total interest before and after recasting, and total savings over the remaining term. A detailed summary tab and a full amortization schedule with monthly and yearly views allow you to examine every payment in both scenarios side by side. Results are formatted for clean PDF export for use in lender discussions or personal financial planning. Completely free, no registration required.

How to Use the Mortgage Recast Calculator Online

Calculating your mortgage recast savings takes just seconds. Follow these simple steps:

• Enter Original Loan Amount – Type the original total mortgage amount at the time the loan was taken out (e.g., $300,000) into the original loan amount field
• Enter Current Principal Balance – Type the current outstanding balance remaining on the mortgage before the lump sum payment (e.g., $250,000) into the current principal field
• Enter Interest Rate – Type the annual mortgage interest rate as a percentage (e.g., 4.5%) into the interest rate field
• Enter Original Loan Term – Type the original mortgage term in years at the time the loan was issued (e.g., 30 years)
• Enter Time Remaining – Type the number of years remaining on the loan from today (e.g., 25 years) into the time remaining field
• Enter Lump Sum Payment – Type the amount you plan to pay as a lump sum toward the principal to trigger the recast (e.g., $50,000) into the lump sum payment field
• Click Calculate Recast – Instantly receive your new monthly payment, monthly savings, total interest savings, and a full before and after comparison
• Review Monthly Payment Savings – See the before and after monthly payment amounts side by side with the dollar saving and percentage reduction displayed prominently
• Review Total Interest Savings – See the total interest payable before and after the recast alongside the total dollar saving over the remaining loan term
• Explore the Summary Tab – View the full loan details including original loan amount, current principal, principal after recast, interest rate, original term, remaining term, and lump sum payment alongside the complete payment comparison
• Explore the Amortization Tab – Toggle between monthly and yearly views of the full amortization schedule showing original payment, original principal, original interest, original balance, recast payment, recast principal, recast interest, and recast balance for every period
• Export to PDF (optional) – Use your browser’s Print → Save as PDF to save a clean single-page record of your recast results for discussions with your lender or personal financial planning

How Mortgage Recasting Works

A mortgage recast reduces the monthly payment by applying a lump sum directly to the outstanding principal and then re-amortising the remaining balance over the unchanged remaining loan term at the existing interest rate.

Step 1 — Calculate Principal After Recast: New Principal = Current Principal Balance − Lump Sum Payment

Step 2 — Calculate New Monthly Payment: Using the standard mortgage amortization formula with the new principal, the same interest rate, and the same remaining term:

New Monthly Payment = New Principal × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1)

Where:

• r = Monthly interest rate (Annual Rate ÷ 12)
• n = Remaining months (Time Remaining × 12)

Step 3 — Calculate Savings: Monthly Savings = Original Monthly Payment − New Monthly Payment Total Interest Savings = Total Interest Before Recast − Total Interest After Recast

Example for a $300,000 original loan, $250,000 current balance, 4.5% interest, 25 years remaining, $50,000 lump sum:

Mortgage Recast vs Refinancing:

Why Use Spluxly’s Mortgage Recast Calculator?

• Full Before and After Comparison – Displays monthly payment and total interest figures for both the original and recast scenarios side by side, making the financial benefit of the lump sum payment immediately visible and quantifiable
• Monthly and Total Savings – Returns both the monthly payment reduction in dollars and percentage and the total interest saving over the remaining loan term, giving homeowners both the short-term and long-term picture of the recast benefit
• Dual Amortization Schedule – Generates a complete period-by-period amortization table showing original and recast payment, principal, interest, and balance columns simultaneously, with a toggle between monthly and yearly views for different levels of detail
• Summary Tab – A dedicated summary panel presents all loan details and payment comparisons in a clean structured format that is easy to read, share with a lender, or include in a financial planning document
• PDF Export Ready – Results are formatted for single-page export via the browser’s Print → Save as PDF function, producing a polished document suitable for lender meetings, financial advisor consultations, or personal record keeping
• Recast vs Refinance Clarity – Supporting content clearly explains the key differences between recasting and refinancing so homeowners can determine which option better suits their financial situation before making a decision
• 100% Free & Instant – No registration, no fees — your full mortgage recast analysis with monthly savings, total interest savings, and complete dual amortization schedule delivered in seconds