Mortgage recast calculator

Currency

Balance owed

Your rate

Years left

Lump sum

Recast fee

Your payment after the recast

$2,025

a month, down $349 from $2,374, with the end date unchanged

Recast saves$50,259

Keeping it saves$145,937

Ends sooner by6 yr 11 mo

Interest still to pay against the size of the lump sum. The dashed line recasts the payment, the solid line holds it. The gap between them at your lump is what the choice is worth.

Putting $50,000 against a $340,000 mortgage at 6.69% with 24 years left cuts the payment from $2,374 to $2,025 a month, a drop of $349, and saves $50,259 in interest after the recast fee. Keeping the old payment instead saves $145,937 and ends the mortgage 6 yr 11 mo early.

How to use this, and the parts people get wrong

A recast keeps your rate and term; the lump sum just shrinks the payment. It is not a refinance.
The fork to study: recast and pocket the smaller payment, or keep paying the old amount and finish years early.
Recasting is a servicer request with a small fee, and not every loan type allows it.

Where the same lump sum goes

The recast hands the saving back as a lower bill: $349 a month freed for 24 years. Keeping the payment holds that $349 against the loan instead, which clears it 6 yr 11 mo early and saves $95,678 more in interest.

$50,259saved by recasting, after the fee

$145,937saved by keeping the payment instead

6 yr 11 mosooner the mortgage ends if you keep it

Lump sums of other sizes

The same balance, rate and years, at every size of lump.

Lump sum	New payment	Recast saves	Keeping the payment saves
$10,000	$2,304	$9,812	$37,037
$25,000	$2,200	$24,980	$84,108
$50,000	$2,025	$50,259	$145,937
$75,000	$1,851	$75,539	$193,061
$100,000	$1,676	$100,819	$229,746
$150,000	$1,327	$151,378	$281,480

Questions people ask

What is a mortgage recast?

You pay a lump sum against the principal and the lender re-amortises what is left over the remaining term at the same rate. The payment falls; the end date stays where it was. On these figures $50,000 off a $340,000 balance takes the payment from $2,374 to $2,025.

Is recasting better than just paying extra?

They save different things. Recasting frees $349 a month for the rest of the term and saves $50,259 in interest. Putting the same lump in and holding the payment where it is saves $145,937 and ends the mortgage 6 yr 11 mo early. The second is the larger number by a factor of about 2.9; the first is the one that helps a stretched month.

Does a recast change my interest rate or my term?

Neither. That is the point of it, and the difference from a refinance: the rate on the note and the final payment date both stay as they are. Only the monthly figure is recalculated.

What does a recast cost?

Most servicers charge a flat administrative fee, commonly between $150 and $500, and set a minimum lump of around $5,000 to $10,000. The fee is an input above and is subtracted from the saving rather than left out of it.

Will my lender allow it?

Conventional loans usually permit one; government-backed loans such as FHA and VA generally do not, and neither do most loans already sold into a security that forbids it. The rule is set by the servicer, so the answer comes from them rather than from arithmetic.

Can I recast more than once?

Many servicers allow it, each time with the fee again. Each recast repeats the same trade: a lower payment now in exchange for the interest that holding the payment would have saved.

Method and sources

Standard level-payment amortisationClosed-form payment, solved directly for the payoff month
30-year fixed mortgage rate, Freddie MacThe rate this page opens with, August 2026. Your own rate replaces it above.

The calculation

The payment is derived from the balance, the rate and the months remaining by the standard level-payment formula, so it matches a loan running to schedule rather than a figure typed in beside it. The recast runs the same formula on the balance after the lump over the same number of months. The third branch keeps the original payment and solves for when the reduced balance reaches zero. Interest under each branch is everything paid beyond the principal owed at the start of that branch.

What these figures do not cover

A fixed rate is assumed for the remaining term.
Escrow for taxes and insurance sits outside the payment shown; a recast changes the principal and interest portion only.
Whether a recast is offered, its fee and its minimum lump are set by the servicer and vary between them.
The comparison prices the money. It does not weigh the value of holding the lump sum in reserve instead.

Last updated August 2026.

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