30-Year Mortgage Recast Calculator
Payment breakdown
Interest & break-even
Total monthly housing cost
Where your money goes over time
If the freed-up cash is invested at 7%, the saved payments grow to about $0 by payoff.
Four ways to use that cash
| Scenario | Monthly P&I | Interest left | Payoff | What happens |
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Show the full amortization schedule (before vs after)
| # | Int. now | Prin. now | Bal. now | Int. recast | Prin. recast | Bal. recast |
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How to use this calculator
- Enter your current loan balance, interest rate, and remaining term.
- Enter the lump-sum amount you plan to pay toward principal.
- Click Calculate to see your new payment, interest savings, and comparison.
About this tool
Made a big payment on a 30-year loan and want the lower monthly bill to match? Enter your balance, rate, remaining term and lump sum to see your new payment, your interest saved, and how a recast stacks up against simply keeping your payment.
A 30-year mortgage is the most common loan in the country, and it's also where a recast frees up the most monthly breathing room — because a 30-year schedule front-loads interest, the early years carry a large balance that a lump sum meaningfully reduces. Recasting re-amortizes that smaller balance across the years you have left, at your existing rate, so the required payment falls without touching your interest rate or extending the term.
What a 30-year recast changes — and what it doesn't
It lowers your required monthly payment and trims total interest along with the balance. It does not change your interest rate, and it does not move your payoff date — a recast on a 30-year loan leaves you finishing on the original schedule, just with a smaller payment. If your aim is to be mortgage-free sooner, the better move is to keep paying your original amount after the recast, which drives the balance down faster.
30-year recast vs refinancing to 15
Homeowners weighing a 30-year recast often also consider refinancing into a 15-year loan. They solve different problems. A 15-year refinance can dramatically cut lifetime interest, but it raises the monthly payment and brings closing costs and a new rate. A recast does the opposite — it lowers the monthly payment on the loan you already have, cheaply, while preserving your rate. If today's rates are higher than yours, the recast is usually the clear winner.
For a shorter loan, see the 15-year recast calculator; to compare against replacing the loan entirely, see recast vs refinance.
30-year recast — FAQ
How does recasting a 30-year mortgage work?
You apply a lump sum to the principal and the servicer re-amortizes the balance over your remaining term at the same rate. Your payment drops; the payoff date and rate stay the same.
Will a recast shorten my 30-year loan?
No. A recast keeps the original payoff date. To finish a 30-year loan early, keep paying your original amount after recasting, or make extra payments instead.
How much can a recast lower my 30-year payment?
It depends on the lump sum and how far into the loan you are. Because a 30-year loan front-loads interest, an early recast frees up meaningful monthly cash flow. Use the calculator to see your figure.
Is a 30-year recast better than refinancing to 15 years?
Different goals. Refinancing to 15 years slashes interest but raises the payment and has closing costs. A recast lowers the payment on your existing 30-year loan for a small fee.
Do the numbers here match my lender?
They're a close estimate using standard amortization. Small differences come from rounding, fees and the exact recast date — confirm the official figure with your servicer.