Mortgage decisions involve real money, so you should be able to see how we got our numbers and how far to trust them. This page explains how we calculate, where our facts come from, what we can't confirm, and how to tell us when something is wrong.
How the numbers are calculated
The calculator and the worked examples in our guides use the standard amortization formula:
Payment = Balance × r ÷ (1 − (1 + r)−n), where r is the annual rate divided by 12 and n is the number of months left.
For example, a $320,000 balance at 6.5% with 27 years left (324 months) gives a payment of $2,097.78. After a $50,000 lump sum, the same formula on $270,000 gives $1,770.00.
From there:
- Interest saved comes from running each scenario month by month until the balance reaches zero, then comparing the total interest paid.
- Fee break-even is the recast fee divided by the monthly payment drop, rounded up to a whole month.
- Payments cover principal and interest only. Taxes, insurance, and mortgage insurance aren't included unless a guide says so.
These are estimates. They assume a fixed rate and on-time monthly payments. Your servicer's figures may differ because of rounding, payment timing, or how it applies the lump sum. Examples in the guides are rounded, and any rate or fee they assume is only an illustration.
Where our facts come from
For rules and definitions, we go to official sources where they exist: government agencies such as the Consumer Financial Protection Bureau, the Department of Housing and Urban Development, the IRS, and the Federal Housing Finance Agency, along with Fannie Mae and Freddie Mac. Each guide lists its sources near the end, with a link and a note on what each one covers.
We open each source and check that it says what we claim before we cite it. Our sources were last checked on November 2, 2026. Rules and web pages change, so follow the link if a detail matters to you.
What we can't confirm
Recasting is mostly governed by each servicer's own policy, so some of what we say has no official source. That includes:
- Recast fees, which we describe as typically $150 to $500
- Minimum lump sums, which we describe as often $5,000 to $10,000
- Processing time, which we describe as about 45 to 60 days
- Which loan types servicers will recast, including our statement that FHA, VA, and USDA loans generally can't be
Treat these as typical patterns, not rules. We don't publish the policies of individual lenders unless they've published them, and your servicer has the final word on your loan.
Who writes our guides
Reamortize is a small, independent site, and our guides don't carry individual bylines. We don't claim professional credentials, and we aren't a lender, broker, or financial advisor. Our guides are general education, not advice about your situation. For that, talk with your servicer or a qualified professional.
Independence and advertising
The site is supported by advertising. No lender pays to be featured or recommended, and advertisers have no say in what we write. Google chooses which ads appear, so an ad isn't an endorsement.
We try to show the honest trade-off even when it makes recasting look less attractive. For example, paying down principal without recasting saves more interest, and we say so.
Corrections and updates
If you find a mistake, a broken source, or a rule that has changed, email contact@reamortize.com with the page and what looks wrong. When a report checks out, we fix the page and change its "Updated" date.