Mortgage Recast Calculator
A recast re-amortizes your loan after a lump-sum payment: the term stays the same, but the monthly payment drops. That is different from paying extra, which shortens the term instead.
Pick a recast when monthly cash flow matters more than total interest saved.
Results update as you type.
How it works
The calculator prices your current balance as one payment, then prices the balance-after-the-lump-sum with the same rate and the same number of months left. The difference is the payment drop.
Formula in both cases: payment = B × r ÷ (1 − (1 + r)^−n). Only B changes, so the end date moves not at all — that is the definition of a recast rather than a payoff strategy.
The lump-sum entry must sit between zero and the balance; a lump sum equal to the balance would retire the loan outright, which is a payoff, not a recast. Servicer recast fees (commonly $100 to $500) are not deducted here.
Example
$320,000 balance · 6.5% rate · 25 years left · $25,000 lump sum
- Balance after the lump sum: $295,000.
- New monthly payment: $1,992, down from $2,161.
- Payment drops by $169 a month — and the payoff year stays the same.
- Compare with the payoff calculator: putting that same $25,000 into extra payments instead cuts the term rather than the payment.
Worked example using the figures above — an illustration, not financial advice. Your loan documents decide the real numbers.
Mortgage Recast Calculator FAQ
What is a mortgage recast?
You pay a lump sum toward principal and the servicer re-amortizes what remains over the same term at the same rate. On a $320,000 loan at 6.5% with 25 years left, a $25,000 recast takes the payment from $2,161 to $1,992.
Does a recast shorten the loan?
No — the end date stays put, and that is the trade. You buy a permanently lower required payment, not an earlier payoff.
Is a recast better than making extra payments?
Extra payments save more interest, because they shorten the loan. A recast saves less interest but lowers the payment you are obliged to make, which is the better tool when income has just dropped.
What does a mortgage recast cost?
Most servicers charge about $100 to $500 and some charge nothing. That is well below refinance closing costs, and unlike a refinance you keep your existing rate — important when current rates are higher than yours.
Can I recast my mortgage more than once?
Usually yes. Lenders commonly set a minimum lump sum, often $5,000, and some limit you to one recast a year. Ask for the recast fee and the minimum in writing before you send the money.
When does a recast actually make sense?
Right after a one-time inflow — a bonus, an inheritance, the sale of another asset — when monthly cash flow is the tight constraint and your existing rate is better than anything on offer today. If the goal is finishing the loan fastest, extra payments beat a recast.
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Last updated October 4, 2026. Every figure is an estimate produced in your browser — see the methodology and its limits.