What Is a Mortgage Recast Calculator?

A mortgage recast calculator is a handy tool that helps you figure out how much your monthly mortgage payment could drop if you make a large, one-time payment (called a lump-sum) toward your loan balance. This process is known as a mortgage recast.

When you recast a mortgage, you don’t change your interest rate or loan term — instead, your lender re-amortizes your loan based on the new, lower balance. That means your monthly payments go down, but you keep the same loan schedule. It’s a great option if you have some extra cash and want to reduce your monthly financial burden without refinancing.

This calculator does all the hard math for you. Just plug in your loan details and the lump-sum amount you’re thinking of paying, and it will show you how your payments change, how much interest you could save over time, and give you a full amortization schedule.

How to Calculate a Recast Mortgage?

Here’s how the calculator works step by step:

1. Enter your original loan balance.
   This is the total amount you borrowed when you first got your mortgage.
2. Enter the annual interest rate.
   This is the rate your lender charges you for borrowing the money — usually something like 3.5% or 4%.
3. Input the number of years left on your mortgage.
   If you have 25 years left to pay off your loan, enter 25. This helps the calculator figure out your full payment schedule.
4. Enter the lump-sum amount you want to pay.
   This is the extra payment you’re planning to make, which will directly reduce your remaining loan balance.
5. Add any recast fee.
   Some lenders charge a small fee (like $250) to recast your mortgage. Enter that here so the calculator can give you a more accurate estimate of your savings.
6. Hit “Calculate”.
   The calculator will instantly show:
   • Your current (old) monthly payment.
   • Your new lower monthly payment after recasting.
   • How much interest you could save over the life of the loan.
   • A chart showing how your balance drops over time.
   • A full month-by-month table of payments.

You can also download the full amortization schedule as a CSV file for your records or to share with your lender.

Terms Used in This Calculator

Here’s a quick rundown of the terms used in the calculator so everything makes sense:

• Original Loan Balance: The amount you borrowed when you first got the mortgage.
• Annual Interest Rate: The yearly rate your lender charges for the loan, usually expressed as a percentage.
• Remaining Term: The number of years you still have left to pay off your mortgage.
• Lump-Sum Payment: A large one-time payment you make toward your loan principal, usually to reduce your monthly payments.
• Recast Fee: A small fee your lender may charge to re-amortize your loan after a lump-sum payment.
• Old Payment: Your current monthly mortgage payment before recasting.
• New Payment: Your reduced monthly payment after the recast.
• Interest Saved: The total amount of interest you’ll save over the remaining loan term by doing the recast.
• Amortization Schedule: A detailed breakdown of each month’s payment, showing how much goes toward principal, how much goes to interest, and what your remaining balance is.