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Mortgage Recast Calculator

Estimate how a lump-sum principal payment could lower a mortgage payment through a recast.

Updated April 11, 2026
Free online tool
Planning and research use

Why this page exists

A recast can lower a mortgage payment without replacing the loan, but the effect depends on how much principal is paid down and how much time is left on the mortgage. This calculator helps homeowners estimate the current payment, the recast payment, and the monthly reduction after a lump-sum principal payment.

Interactive tool

Run the estimate

Enter your numbers and read the result first, then use the sections below to understand what affects the outcome.

Calculator

Mortgage recast calculator

Estimate how a lump-sum principal payment could lower a mortgage payment through a recast.

Result

$1,787.50

Estimated recast payment based on reducing the current balance with a lump-sum principal payment while keeping the same remaining term and rate.

New estimated recast payment$1,787.50

Current estimated payment$1,953.01

Monthly payment reduction$165.51

Balance after lump-sum payment$270,000.00

$25,000.00 applied to principal lowers the balance from $295,000.00 to about $270,000.00.
At the same 6.10% rate and remaining term, the monthly payment drops by about $165.51 in this recast estimate.
This is different from a refinance because it assumes the existing mortgage stays in place and only the payment is recalculated on the lower balance.

This is a planning estimate. Real lender rules, recast fees, eligibility, and servicer timing can change whether a mortgage can actually be recast and what payment results.

Planning note

Last updated April 11, 2026. Use this tool to compare scenarios and plan ahead, then confirm important details with the lender, employer, insurer, contractor, or other qualified provider involved in the final decision.

How it works

What the calculator is doing

Enter the current loan balance, interest rate, remaining term, and lump-sum principal payment.

The calculator estimates the current payment from the existing balance and remaining term.

It then recalculates the payment on the lower post-payment balance using the same rate and remaining term.

Understanding your result

The monthly reduction is usually the most useful part of the result because it shows what the recast is buying in day-to-day cash flow. That makes it easier to compare a recast idea with other uses for the lump-sum money.

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Examples

Ways people use this tool

Example scenarios help turn a quick estimate into a more useful comparison or planning step.

Compare making a large principal payment or not

The calculator shows how much the monthly payment might drop if the loan is recast after a lump-sum payment.

Estimate a payment change without refinancing

A recast estimate can help show whether a lower payment is possible without replacing the mortgage entirely.

Use a principal windfall more deliberately

The estimate helps turn a bonus, home sale, or inheritance amount into a more concrete mortgage-payment comparison.

FAQ

Common questions

How is a recast different from a refinance?

A recast keeps the existing mortgage in place and recalculates the payment after a lump-sum principal payment, while a refinance replaces the loan with a new one.

Why does the payment fall after a recast?

Because the remaining balance is smaller, so the loan payment can be recalculated over the same remaining term and rate on less principal.

Does every lender allow recasting?

No. Recast rules, eligibility, and any fees can vary by lender and loan type, so this tool is a planning estimate only.

Related tools

Keep comparing

Use these related tools to compare nearby scenarios, check a second estimate, or keep narrowing down the right decision.

Home ToolsUpdated April 11, 2026