Mortgage Recast Calculator With Amortization

Most Homeowners Have Never Heard of "Recasting" — Here's What It Actually Is

That gap in awareness isn't an accident. Refinancing gets marketed relentlessly — lenders run ads for it every time rates twitch. Recasting gets almost no marketing at all, because it's a low-fee service rather than a new loan a lender can profit from originating. So the mix-up is understandable: both involve a call to your lender, both can lower your monthly payment, and both sound like paperwork-heavy financial events. But a recast is neither a new loan nor a rate negotiation. It's closer to a bookkeeping request than a financial product.

Here's precisely what happens. You make a lump-sum payment toward your loan's outstanding principal balance — often from a bonus, an inheritance, investment gains, or leftover proceeds from selling a previous home. Your lender then re-amortizes your existing loan: same interest rate, same number of months remaining, but recalculated against the new, smaller balance. Because you owe less and you're still paying it off over the same span of time, your required monthly payment goes down. Nothing else about the loan changes — no new promissory note, no new closing disclosure, no new rate lock, no reset payoff clock.

Lenders charge for this because someone still has to manually process the request and update your amortization schedule on file — typically a flat $150 to $500 fee, paid once. Compare that to refinancing, which involves a full loan application, often an appraisal, underwriting, a hard credit pull, and 2-5% of your loan amount in closing costs. A recast is about as close to a "quiet" change as your mortgage will ever get: same lender, same loan, smaller bill.

Recast vs. Refinance vs. Extra Payments: Three Different Tools

These three strategies all reduce what you owe over time, but they solve different problems and none of them is strictly "better" — the right one depends on what you're holding (a lump sum vs. a bit of extra monthly cash flow) and what you want to change (your payment vs. your payoff date vs. your rate). A recast is built for people sitting on a lump sum who like their current rate and just want breathing room in their monthly budget. A refinance is built for people whose rate no longer makes sense, or who want to change their term entirely. Extra payments are built for people without a single lump sum who want to chip away consistently and finish early instead of paying less each month.

One nuance worth spelling out: you can technically send a lump sum toward principal without ever requesting a recast. If you do that, your servicer applies it to your balance but keeps billing you the original payment amount — which means the loan simply pays off earlier, exactly like a recurring extra payment would. A recast is the additional, optional step of asking the lender to re-amortize and formally lower your required bill instead. Same money, different outcome, and it's your call which one you want.

Who Actually Qualifies for a Mortgage Recast

Because a recast doesn't involve underwriting, eligibility has nothing to do with your credit score or income — it comes down entirely to your loan type and your individual servicer's policy. Conventional loans — mortgages bought by Fannie Mae or Freddie Mac — are by far the most common candidates for recasting. Fannie Mae's own Selling Guide documents how servicers apply a borrower's principal curtailment and, where a modification agreement is used, reduce the monthly payment on the loans it purchases, which is the underlying mechanism a conventional recast relies on.

Government-backed loans are the notable exception. FHA, VA, and USDA loan programs generally do not offer a recast option under their servicing rules, regardless of how large a lump sum you have available — this is consistent across FHA guidance, VA lender education resources, and mainstream mortgage-servicer explainers. If you hold one of these loan types and want a lower monthly payment without refinancing, your realistic options are a large extra principal payment (which shortens your payoff date rather than lowering your bill) or, if today's rates support it, a full refinance.

Even within conventional loans, individual servicers set their own minimum lump-sum thresholds and processing fees, and some may decline to recast certain jumbo, portfolio, or adjustable-rate products. Before you count on a recast, call your servicer's loss-mitigation or loan-servicing line and confirm, in writing, that your specific loan qualifies and what their minimum curtailment amount is.

Worked Example: Recasting a $280,000 Balance With a $30,000 Lump Sum

The defaults loaded into the calculator above are a realistic scenario: a $280,000 remaining balance, a 6.5% rate, and 25 years (300 months) left on the loan. Run through the standard amortization formula, that balance carries a principal-and-interest payment of $1,890.58 a month.

Now say a work bonus lets you put $30,000 toward principal and request a recast. Your balance immediately drops to $250,000. Your lender re-amortizes that $250,000 over the exact same 300 months remaining, at the exact same 6.5% rate, and your new required payment comes out to $1,688.02 a month — a reduction of $202.56 every month, for the rest of the loan. Multiplied across the remaining 25 years, that's roughly $60,769 less paid out in principal-and-interest installments than if you'd kept the original $1,890.58 payment, for a one-time processing fee typically under $500.

Two things are worth noticing in that math. First, the $30,000 you put in isn't "spent" — it's equity you already owned in the home, just moved from a side account into your loan balance; the real benefit of the recast is the $202.56 a month of freed-up cash flow, not new money created from nowhere. Second, unlike a refinance, there's no break-even period to calculate against closing costs — the $150-$500 fee is trivial next to the payment reduction, and the savings start on your very next bill. Try your own balance, rate, remaining term, and lump sum in the calculator above to see your specific numbers.

Methodology and Sources

Every number in this mortgage recast calculator with amortization comes from the same standard fixed-rate formula lenders use to generate an amortization schedule: M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where P is the loan balance, r is the interest rate divided by 12, and n is the number of monthly payments remaining. A recast runs that formula twice against the same rate and the same n — once against your old balance, once against your new, lower balance after the lump sum — and the difference between the two results is your monthly savings. For the full derivation and every variable our calculators support, see our mortgage amortization calculation methodology page.

The eligibility claims on this page — that conventional, Fannie Mae/Freddie Mac-backed loans are the standard candidates for recasting, while FHA, VA, and USDA loans typically are not — are documented in Fannie Mae's Selling Guide, Section B2-1.5-05 on Principal Curtailments, which governs how servicers apply lump-sum curtailments and modification agreements on the conventional loans Fannie Mae purchases. As always, loan-level eligibility and fees are ultimately set by your individual servicer, so confirm your specific terms before making a lump-sum payment.

Curious how a recast stacks up against your other options? Model a rate change on our refinance amortization calculator, see how recurring extra payments compare on our mortgage calculator with extra payments, or check out our balloon mortgage amortization calculator if you're evaluating a short-term loan structure instead. For the full picture of how any mortgage amortizes over time, start from our mortgage amortization calculator homepage.