Mortgage Recast Calculator
Payment breakdown
Interest & break-even
Solve it backwards: aim for a payment
Know how much lower you want the bill? See the principal it takes to get there.
Total monthly housing cost
Where your money goes over time
Assuming the freed-up 7% is invested each month, the saved payments grow to about $0 by payoff. Edit the return rate in the panel above.
Four ways to use that cash
| Scenario | Monthly P&I | Interest left | Payoff | What happens |
|---|
Show the full amortization schedule (before vs after)
| # | Int. now | Prin. now | Bal. now | Int. recast | Prin. recast | Bal. recast |
|---|
How to use this calculator
- Enter your current loan balance, interest rate, and remaining term.
- Enter the lump-sum amount you plan to pay toward principal.
- Click Calculate to see your new payment, interest savings, and comparison.
About this tool
Just came into a lump sum? Put your numbers in below and see exactly what a principal payment does to your monthly bill — the new payment, the interest you'd save, and whether it beats refinancing or simply investing the cash.
How a mortgage recast calculator works
Recasting keeps your loan exactly as it is — same rate, same payoff date — and only re-spreads the smaller balance across the payments you have left. That single change is what lowers the bill.
Pay down principal
You send the servicer a large one-time payment marked principal only. The balance drops the day it posts.
Request the recast
The lender re-amortizes the reduced balance over the remaining term. Most charge a small flat fee to do it.
Pay less every month
A new, lower principal-and-interest payment begins — usually within one to two billing cycles.
Rate & term stay put
No credit check, no closing costs, no reset clock. The interest rate and maturity date are untouched.
The formula this tool uses
The new payment is the standard amortization equation applied to your reduced balance. If B is your current balance and L is the lump sum, the recast payment M′ is:
r = annual rate ÷ 12 (monthly rate)
n = payments remaining
M′ = B′ × [ r(1 + r)ⁿ ] ÷ [ (1 + r)ⁿ − 1 ]
Interest saved is the difference between the interest you'd pay on the original schedule and the interest on the recast schedule. The tool also runs three alternatives side by side — keep paying the old amount, refinance, or invest the cash — because the lowest monthly payment isn't always the cheapest choice over the life of the loan.
What it can't tell you
These are estimates, and a few things sit outside the math on purpose. Your servicer sets the real fee and the minimum principal required. Adjustable-rate loans, and any missed or partial payments, will shift the numbers. And a recast never touches the escrow portion of your bill, so the "total housing cost" figure only moves if your taxes or insurance change independently. Treat the output as a well-informed starting point for the call you'll make to your lender.
Common situations for recasting
Almost everyone who lands here has money in hand and a decision to make. The details of where the money came from change the right answer.
Sold a previous home
Proceeds from a sale are the classic recast trigger — drop the balance on the new loan without refinancing at a higher rate.
Year-end bonus or RSUs
A large, one-off cash event that you'd rather turn into lower fixed costs than leave sitting idle.
Inheritance or windfall
Money you want working against a low-rate mortgage — but only if it beats keeping it invested. Run both here.
Locked in a low rate
Refinancing would raise your rate, so a recast is the only way to cut the payment while keeping the rate you have.
Rental cash-flow tuning
Investors recast to lift monthly cash flow on a property without triggering a new underwrite.
After extra payments piled up
You've been overpaying and want the balance you've built to actually lower the required payment.
What a recast looks like in real numbers
Say you owe $300,000 at 6.5% with 25 years to go, and you apply $50,000 to principal. Here's the before-and-after the calculator produces:
| Measure | Before recast | After recast | Difference |
|---|---|---|---|
| Balance | $300,000 | $250,000 | −$50,000 |
| Monthly P&I | $2,025.62 | $1,688.02 | −$337.60 |
| Interest over the loan | $307,686 | $256,405 | −$51,281 |
| Payoff date | Unchanged | Unchanged | Same |
| Interest rate | 6.5% | 6.5% | Same |
The payment falls by $337 a month. But notice the twist the tool surfaces: if you instead pay the same $50,000 and keep making the old $2,025 payment, the loan clears roughly eight years early and total interest drops far more. Lower payment or lower lifetime cost — the comparison table above shows both so you can pick on purpose.
Data & authority
The math here is standard mortgage amortization — the same equation your lender uses. Policy details (minimum principal, fees, eligible loan types) vary by servicer and change over time, so we point you to primary sources rather than repeating figures that may be stale:
- The U.S. Consumer Financial Protection Bureau (consumerfinance.gov) explains borrower rights around payment application and loan servicing.
- Individual servicers — Chase, Wells Fargo, Rocket Mortgage, Bank of America and others — publish their own recast terms. Our lender rules guide summarizes them with a "last reviewed" date and links back to each source.
- Fannie Mae and Freddie Mac servicing guidelines shape which conventional loans can be recast.
Guies Roc Blanc is an independent tools publisher. We are not a lender, broker or financial advisor, and nothing here is personalized financial advice. Always confirm terms directly with your loan servicer before sending money.
Mortgage recast questions, answered
What is a mortgage recast?
A recast (also called re-amortization) is when you make a large lump-sum payment toward your principal and your lender recalculates your monthly payment based on the new, lower balance. The interest rate and the remaining term stay the same, so only the principal-and-interest portion of your payment goes down.
How is the new payment calculated?
Your lender takes the reduced balance and spreads it over the number of payments you have left, at your existing rate, using the standard amortization formula. This calculator runs the same equation, so the estimate should be close to your servicer's official figure barring rounding and any fee.
How much do I have to pay to recast?
Most lenders set a minimum principal reduction, commonly in the range of $5,000 to $10,000, and some require the payment to bring the balance down by a set percentage. The exact minimum is the servicer's call — confirm it before you plan around a specific number.
What does a recast cost?
Recast fees are usually a flat charge, often $0 to $500. That's dramatically cheaper than refinancing, which carries closing costs of several thousand dollars. The calculator shows how quickly a fee is recovered through lower payments.
Does recasting lower my interest rate?
No. This is the key difference from refinancing. A recast keeps your current rate untouched — which is exactly why it's attractive when you're holding a low rate you don't want to lose.
Does a recast shorten my loan term?
By default, no — the payoff date stays the same and your payment drops. If you'd rather shorten the loan, don't recast: keep paying your original (higher) amount on the reduced balance and you'll finish early. The comparison table shows both paths.
Recast or refinance — which saves more?
If current rates are lower than yours, refinancing can save more despite closing costs. If your rate is already low, a recast almost always wins because it's cheap and keeps your rate. Our recast vs refinance guide walks through the break-even in detail.
Should I recast or just invest the cash?
That depends on your rate versus expected investment returns. The calculator projects both: the guaranteed interest you'd save by recasting, and the potential value of investing the same money. Compare the two figures — and weigh the certainty of debt reduction against market risk.
Which loans can be recast?
Most conventional fixed-rate mortgages qualify. Government-backed loans — FHA, VA and USDA — generally cannot be recast. Jumbo and investment-property loans depend on the lender. Verify your loan type with your servicer.
Can I recast more than once?
Often yes, though some servicers cap the number of recasts over the life of the loan or require a minimum time between them. Ask your lender about their specific policy.
Do I pay the lump sum before or after requesting the recast?
Typically the principal payment must post first, then you request the re-amortization. Mark the payment "principal only" so it isn't applied to future installments, and confirm the servicer's order of operations.
Will my property taxes and insurance go down too?
No. A recast only affects principal and interest. The escrow portion — taxes, homeowners insurance, PMI, HOA — is set separately and doesn't change because you paid down the balance.
Does a recast remove PMI?
Not automatically. PMI removal depends on your loan-to-value ratio and your servicer's rules. A large principal payment can help you reach the threshold to request removal, but that's a separate process from recasting.
How long does a recast take?
After the principal payment posts and you submit the request, most recasts complete within one to two billing cycles. Watch your next statement to confirm the new payment and that the money hit principal.
Is my data saved anywhere?
No. Every calculation runs in your browser. Nothing you type is sent to a server or stored, and the shareable link simply encodes your inputs in the URL so you can revisit or share a scenario.
Is this the same figure my lender will give me?
It should be very close. Small differences come from rounding, the exact day your payment posts, and the recast fee. Use this to decide whether to proceed, then get the official number from your servicer.
What homeowners say
"Finally a recast tool that shows the invest-instead option next to the payment drop. That comparison changed my mind about where the bonus went."
"I didn't realize paying the lump without recasting would pay us off eight years early. The side-by-side made it obvious."
"Clear on the fee break-even and honest that it's not the lender's official number. Called Chase with the figures ready to go."
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