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What Is a Mortgage Recast?
A mortgage recast, sometimes called a loan re-amortization, is a simple lender service that lowers your monthly mortgage payment after you make a substantial lump sum payment toward principal. Your servicer recalculates the monthly payment using the new, smaller balance, the original interest rate, and the original remaining term. The payoff date stays the same, the interest rate stays the same, and you do not have to refinance, requalify, or close on a new loan. In exchange, you pay a modest recast fee, usually $150 to $500. Many homeowners first search for this as a mortgage recasting calculator or a recast mortgage calculator, since recasting and re-amortizing describe the exact same lender process from two different angles.
The mortgage recast calculator above takes the math out of the decision. You enter your current balance, interest rate, remaining months, and the lump sum you plan to put down. The tool returns your new monthly payment, the dollar amount saved every month, the total interest saved across the remaining life of the loan, and the break-even on the recast fee. Most users break even on the fee within one to three months; the rest is pure cash flow improvement for the years that remain on the mortgage. Run it as a mortgage reamortization calculator whenever a lump sum lands in your account and you want a fast answer before calling your servicer.
Recasting is a niche tool, but a powerful one for the right situation. If you just sold another property, received an inheritance, vested stock, or had a windfall year of self-employment income, a recast turns that lump sum into a permanent monthly cash flow reduction without surrendering a low interest rate. According to the Consumer Financial Protection Bureau, monthly mortgage payments are typically the largest single line item in a household budget, so even a $300 monthly reduction has a meaningful effect on long-term financial flexibility.
Recast vs Refinance: Which One Should You Use?
The recast vs refinance calculatorquestion comes up constantly for anyone comparing a mortgage recast calculator against a full refinance, and the answer hinges on one variable: how does your existing interest rate compare to today's market rate? If your current rate is at or below the prevailing rate, a recast is almost always the better move. You keep your favorable rate, you skip the $5,000 to $15,000 closing costs of a refinance, and you avoid the credit check, appraisal, and underwriting timeline. A recast typically processes in 30 to 60 days compared to 30 to 60 days for a refinance, but for far less money and far less paperwork.
A refinance wins, on the other hand, when market rates have dropped meaningfully below your current rate (typically 0.75 percentage points or more) and you plan to stay in the home long enough to recover closing costs. If you are considering a refinance, run your numbers through our refinance calculator and the mortgage refinance break-even calculator to model the payback period. According to Investopedia's mortgage recast guide, the recast is widely under-recognized because most homeowners default to thinking about refinancing when rates change, even when their existing loan is already cheaper than the market.
A third option many borrowers overlook is doing nothing structural and instead redirecting the lump sum into a higher-yielding investment account. If your mortgage rate is 3 percent and Treasury yields are 4.5 percent, the math may favor keeping the mortgage as-is and investing the lump sum. The mortgage recast calculatoron this page does not model investment opportunity cost, so always weigh the calculated savings against the after-tax return you could earn elsewhere with the same cash.
When Mortgage Recasting Makes Sense
Mortgage recasting, the process behind every mortgage recasting calculator result, makes the most sense in five common scenarios. First, when you sell a previous home and want to apply the proceeds to your new mortgage without giving up the new mortgage's low rate. Second, when you receive a large inheritance, settlement, or bonus and want to permanently reduce housing costs. Third, when a divorce settlement requires one spouse to buy out the other's equity and you want to keep the existing loan intact. Fourth, when you have stock vesting events (RSU or ESPP) that generate large taxable cash flows you want to deploy productively. Fifth, when your monthly cash flow is tight and freeing up several hundred dollars per month would relieve real financial pressure.
Recasting is less compelling if your remaining loan term is short, say, under five years, because the monthly payment reduction is small relative to the lump sum committed. It is also weak if you can afford to keep paying the higher payment and would simply rather end the loan early; in that case, applying the lump sum to principal without recasting will save you significantly more total interest because the loan terminates years sooner. Try both scenarios side by side in the lump sum mortgage payment calculator above to see the gap.
One scenario worth flagging: government-backed loans (FHA, VA, USDA) generally cannot be recast. If you have one of these loans and want a lower payment, you will need to pursue a streamline refinance instead. According to Bankrate's mortgage recasting overview, most conventional loans, jumbo loans, and portfolio loans allow at least one recast per loan over its lifetime, but you must call your servicer directly to confirm eligibility before assuming you qualify.
Recasting vs Paying Extra Principal: The Real Tradeoff
The cleanest way to understand the value of a recast is to compare it against just applying the same lump sum to principal without recasting, a feature this loan recast calculator handles directly in its side-by-side comparison. Run the same inputs through the recast mortgage calculator view and the extra-principal view back to back so the tradeoff is visible in dollars, not just theory. Both strategies use the same lump sum, but the outcome differs in a specific way. With a recast, your monthly payment drops and the payoff date stays the same. With extra principal applied directly (and no recast), the monthly payment stays the same and the loan terminates earlier, often years earlier on a 30-year mortgage. The early payoff means you avoid years of interest payments that would otherwise accrue, so the absolute interest savings are larger in the extra-principal scenario.
Here is the practical interpretation. A recast trades total interest savings for monthly cash flow relief. Extra principal trades monthly cash flow for total interest savings. Neither is universally better. They serve different financial goals. If you need or want lower monthly cash outflow (because you are approaching retirement, want flexibility for childcare, or are reducing reliance on a high income), recast. If you can comfortably afford the current payment and your goal is to be debt-free as quickly as possible, apply the lump sum to principal without recasting. To go deeper into payoff acceleration, our biweekly mortgage calculator shows another path to early payoff using payment frequency rather than a single lump sum.
A hybrid approach is also viable: recast to lower the monthly payment, then continue paying your previous (higher) payment amount voluntarily. This gives you the insurance-policy flexibility to drop back to the lower required payment whenever cash is tight, while still accelerating the payoff during normal months. The math is slightly worse than a pure extra-principal approach because of the recast fee, but the flexibility may be worth $250 to you. For more strategies across the full property ownership lifecycle, see our real estate calculators section.
How to Request a Mortgage Recast from Your Servicer
Requesting a mortgage re-amortization, the process this mortgage reamortization calculator models, is one of the simpler transactions you will ever do with a lender. Step one is identifying your servicer, the company you send your monthly payment to, which may or may not be the original lender. Look at your most recent mortgage statement or log into your online account. Step two is calling the servicer's customer service line and asking three specific questions: Is my loan eligible for a recast? What is the minimum lump sum required? What is the recast fee? Most representatives can answer these in five minutes.
Step three is requesting the recast in writing; most servicers have an online form or a one-page recast request agreement they will email you. You sign it, return it, and arrange to send the lump sum payment along with the recast fee. The servicer applies the lump sum to principal, recalculates the monthly payment using the new balance and the remaining term, and issues a new amortization schedule. The new lower payment typically takes effect the month following the recast; be sure to update your autopay amount if you have one configured. The total elapsed time from initial call to new lower payment is usually 30 to 60 days.
One practical note: always confirm in writing that the lump sum will be applied to principal (not to a future month's payment) before sending money. Many servicers default to applying ad-hoc payments forward as prepayments unless you specifically instruct otherwise. Most servicers also limit borrowers to one or two recasts over the life of the loan, so pick your moment carefully. If you anticipate multiple windfalls over the next few years, consider waiting until you can pool them into a single, larger recast. The mortgage recast calculator on this page makes it easy to test different lump sum sizes to find the sweet spot before you commit, and doubles as a loan recast calculator for second homes and investment property mortgages that follow the same re-amortization rules.