Mortgage Recast Calculator

A recast spreads a lower mortgage balance over the remaining term. MiniWebtool’s Mortgage Recast Calculator models the new payment after a lump sum and compares recasting with prepayment alone or refinancing, including fees and interest totals.

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Help me understand MiniWebtool's Mortgage Recast Calculator: https://miniwebtool.com/mortgage-recast-calculator/. What can I use it for, what inputs or settings do I need, and how do I use it and understand the output? Walk me through one simple example. Use this page as your source and answer in English.

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Mortgage Recast CalculatorTry it now — free ▼

$30,000 recast on $285,000 at 6.5%: $1,868.33 → $1,671.67

Enter the balance, rate, original term and months paid, the lump sum and recast fee. The result gives the new payment and compares a refinance.

⚡ Quick start — pick a scenario to autofill

📋 Your current loan

Current loan balance $

Current interest rate %

Original loan term (years)

Months already paid

💵 The lump-sum recast

Lump-sum principal payment $

Recast servicing fee (typically $150–$500) $

🔁 Optional refinance comparison (leave blank to skip)

Refinance rate %

Refinance closing costs $

Embed Mortgage Recast Calculator Widget

About Mortgage Recast Calculator

The Mortgage Recast Calculator tells you exactly what your monthly principal-and-interest payment becomes after a lump-sum principal payment that triggers a re-amortization. Unlike a refinance, a recast keeps your interest rate, your original payoff date, and your loan account number — only the balance and the monthly payment change. Most online calculators stop at the new payment. This one walks the whole decision: how the savings compare to a prepay-only strategy that finishes the loan faster, how a refinance at today's rate would stack up, when the recast servicing fee breaks even, and how the new payment scales with different lump-sum sizes.

At a Glance

Mortgage Recast Calculator shows the new monthly principal-and-interest payment after a lump-sum principal payment is recast. It compares recasting with prepaying only and with refinancing, including fees and total interest.

Mortgage Recast Calculator: features at a glance
Feature	What you get	Good for
Loan and lump-sum inputs	Enter current balance, interest rate, original term, months already paid, lump-sum payment and the recast servicing fee.	Borrowers with a bonus, inheritance or sale proceeds
New payment	Shows the recalculated monthly P&I payment. The rate and the original payoff date stay the same, and an animated timeline shows it.	Seeing how much the monthly bill drops
Three-way comparison	Compares do-nothing, recast, prepay-only and, if you enter a refinance rate and closing costs, refinance, using the same lump sum.	Choosing between lower payments and faster payoff
Fee break-even	Shows how many months of payment savings it takes to recover the recast servicing fee.	Judging whether the lender's fee is worth paying
Lump-sum sensitivity	Bars show the new payment at 25%, 50%, 75%, 125%, 150% and 200% of the lump sum you entered.	Deciding how much of a windfall to apply
Balance chart	A chart of remaining balance over the rest of the term, with a curve for each strategy, plus total interest saved.	Seeing how the strategies diverge over time
Quick-start presets	One click loads a first-home, mid-life, windfall or downsizer scenario.	Trying realistic numbers before entering your own

What makes this calculator different

Same finish line, smaller steps

An animated timeline shows your remaining months as bars, with a 🏁 flag at the payoff date that does not move after a recast. Recasting shrinks every bar; prepay-only keeps the bar height but moves the flag earlier. Two visuals, one truth.

Three strategies side-by-side

Most recast calculators show only one number. We compare Do-nothing, Recast, Prepay-only, and (optionally) Refinance using the same lump sum — so you see the cash-flow trade-off, not just the new payment.

Break-even on the recast fee

The lender charges a flat $150–$500 servicing fee. We tell you exactly how many months of savings it takes to recover that fee. Pure-win territory starts after that month.

Lump-sum sensitivity bars

A grouped bar chart shows what your new payment would be at 25%, 50%, 75%, 125%, 150%, and 200% of your entered lump sum — useful when you are choosing how much of a windfall to deploy.

Honest total-interest math

We compute the actual total interest under each strategy — not just the headline payment — so you can see why prepay-only saves more interest than recast even though the recast has the lower monthly bill.

Four real-world quick starts

One click loads a first-home borrower 3 years in, a mid-life refinance candidate 7 years in, a borrower with a big bonus or inheritance, or a downsizer who just sold their old home — so you can play with realistic numbers before plugging in your own.

How to use the Mortgage Recast Calculator

Pick a quick-start scenario — first home, mid-life, windfall, or downsizer — to autofill realistic numbers, or enter your own loan from scratch.
In the loan pane, enter your current balance, your original loan term in years (typically 30), the months you've already paid, and your current interest rate.
In the recast pane, enter the lump-sum amount you want to apply to principal and the recast servicing fee your lender charges (default $250 if unsure).
Optionally, in the refinance pane, type a refinance rate and closing-cost estimate to see how a full refi compares to a recast on the same lump sum.
Click Calculate. The headline shows your new monthly P&I; the timeline visualizes the "same finish line, smaller steps" insight; the strategy grid compares all three (or four) paths; the chart plots remaining balance over time; and the sensitivity bars show how the new payment scales with lump-sum size.

The math under the hood

The fixed-rate amortization formula gives you the level monthly payment that pays off a balance $ B $ at monthly rate $ r $ over $ n $ months:

$ \text{PMT} = \dfrac{B \cdot r}{1 - (1 + r)^{-n}} $

A recast applies a lump sum $ L $ directly to principal, leaving the rate $ r $ and remaining months $ n $ unchanged. The new payment is computed on the smaller balance:

$ \text{PMT}_{\text{recast}} = \dfrac{(B - L) \cdot r}{1 - (1 + r)^{-n}} $

Because both numerator and denominator use the same $ n $, the payoff date does not change — the monthly bill just shrinks in proportion to how much of $ B $ the lump sum replaced.

For the prepay-only comparison, the lump sum is applied but the monthly payment stays at the original level. The loan finishes early, in $ n^{\star} $ months:

$ n^{\star} = \dfrac{-\ln\left(1 - \dfrac{(B - L) \cdot r}{\text{PMT}_{\text{orig}}}\right)}{\ln(1 + r)} $

Break-even on the recast servicing fee $ F $ is the number of months of monthly savings needed to recover the fee:

$ \text{break-even} = \left\lceil \dfrac{F}{\text{PMT}_{\text{orig}} - \text{PMT}_{\text{recast}}} \right\rceil $

Recast vs Prepay vs Refinance — quick decision table

Mortgage Recast Calculator: Recast vs Prepay vs Refinance — quick decision table
Question	Recast	Prepay-only	Refinance
Changes interest rate?	No	No	Yes
Changes loan term?	No	No (finishes early)	Yes (new term)
Lowers monthly payment?	Yes	No	Usually, depends on rate
Out-of-pocket cost	$150–$500 fee	$0	2–6% of balance in closing costs
Underwriting / appraisal?	No	No	Yes
Available on FHA / VA / USDA?	Generally no	Yes	Yes
Best for	Cash-flow relief, freeing budget	Saving total interest, faster payoff	Capturing a meaningfully lower rate

When does recasting beat prepaying?

Both strategies use the same out-of-pocket lump sum. The difference is what you do with the monthly savings after that. If your goal is cash-flow relief now — for example, you want a smaller mortgage bill so you can max out a retirement account, fund tuition, or take on a slower-paying career — recasting wins. If your goal is to minimize total interest and pay the loan off faster, prepay-only wins because every dollar of your unchanged monthly payment after the lump sum goes further toward principal.

There is a hidden third option: recast and then keep paying the original amount. After recasting, voluntarily continue paying your old, higher monthly amount. That gives you the cash-flow safety net of a lower required payment, but you still finish the loan early like prepay-only. The lender will apply the overage to principal automatically. This is the strategy financial planners often recommend for higher-income households.

Common questions about recasting

What is a mortgage recast?

A mortgage recast is a re-amortization. You make a lump-sum payment toward principal and the lender recalculates your monthly principal-and-interest payment over the remaining original term at the same interest rate. The loan is not refinanced and the payoff date does not change, only the monthly payment shrinks.

How is recasting different from prepaying or refinancing?

Prepaying means sending extra money to principal while keeping the same monthly payment. The loan finishes earlier but the monthly bill does not change. Refinancing means replacing the existing mortgage with a new loan at a new rate and term, with full closing costs and underwriting. Recasting sits between the two: a small fee, no underwriting, same rate, same payoff date, but a lower monthly payment.

How much is a mortgage recast fee?

Most US lenders charge a flat servicing fee between $150 and $500, with $250 being typical. The fee is one-time and is paid at the time of the recast. The break-even calculation in the result tells you how many months of monthly savings cover the fee.

What is the minimum lump-sum amount for a recast?

Most servicers require a minimum lump-sum of $5,000 to $10,000 before they will recast. The lump must be applied directly to principal (not to your escrow or to the next month's payment). Confirm the minimum with your servicer before applying funds.

Does a recast change my interest rate?

No. The rate stays exactly the same. If your goal is a lower rate you need to refinance instead. Recast only changes the balance and therefore the monthly amount, not the rate or the term.

Can FHA, VA, or USDA loans be recast?

Generally no. Government-backed loans (FHA, VA, USDA) and most jumbo loans typically cannot be recast. Recast availability is most common on conforming conventional Fannie Mae and Freddie Mac loans. Ask your servicer for written confirmation.

Will a recast hurt my credit score?

No. A recast does not require a new loan application, hard credit pull, appraisal, or underwriting. The account number and terms stay the same. Your credit report sees a lower balance and a lower monthly payment, both of which generally help.

When does a recast make more sense than prepaying?

Recast wins when you want cash-flow relief now, for example to reduce a stretched monthly budget or free up cash for other investments. Prepaying wins when your goal is to minimize total interest and you do not need a smaller monthly payment. The two strategies produce the same final payoff date if you keep paying the original payment after the recast.

Reference this content, page, or tool as:

"Mortgage Recast Calculator" at https://MiniWebtool.com/mortgage-recast-calculator/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: 2026-05-14

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