Mortgage Recast Calculator

A mortgage recast lets you make a large lump-sum principal payment, then re-amortize the lower balance over the same remaining term — lowering your monthly payment while keeping your rate and payoff date. See how much your payment would drop.

Your details

Current loan balance$Lump-sum payment$The one-time principal payment applied before re-amortizing.Interest rate%Remaining termYears left on the loan — a recast keeps this the same.

New monthly payment

$1,610.75

Current monthly payment: $1,932.90
Monthly saving: $322.15
New balance: $250,000.00

New payment vs saving

New payment: $1,610.7583%
Monthly saving: $322.1517%

New monthly payment$1,610.75

Formula

The payment is recomputed on the reduced balance: M = P·r(1+r)^n / ((1+r)^n − 1), where P is the balance after the lump sum, r the monthly rate, and n the remaining number of payments. Unlike extra payments (which shorten the term), a recast keeps the term and cuts the monthly amount.

Frequently asked questions

How is a recast different from refinancing?⌄

A recast keeps your existing loan, rate, and term — it just lowers the payment after a lump-sum principal reduction, usually for a small fee. Refinancing replaces the loan entirely, with new closing costs and possibly a new rate.

Does a recast save on interest?⌄

Yes — because the balance is lower, you pay less total interest. But since the term stays the same, the monthly relief is the headline benefit; paying extra without recasting saves more interest by shortening the term.

Sources & methodology

Re-amortizes the balance after the lump sum over the same remaining term at the same rate. Excludes recast fees and escrow. Confirm your lender allows recasting.

•Consumer Financial Protection Bureau — mortgages — CFPB

Last updated: 2026-07-20

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