About this calculator
Choosing between a fixed and adjustable-rate mortgage is not a one-size-fits-all decision. It depends on how long you plan to stay, your risk tolerance, and how you think rates will move. This calculator runs both scenarios side by side so the tradeoff is visible, not theoretical.
What it shows you
- Monthly payment: fixed vs. ARM initial rate
- ARM adjustment scenarios (worst case, flat, best case)
- Total interest paid over any time horizon
- Break-even point where fixed-rate total cost is lower
- Full amortization schedule for both loan types
What you'll enter
- Loan amount, interest rate, and term
- Closing costs, which set the APR it shows
- ARM fixed period and adjustment period
- Initial, periodic, and lifetime rate caps, and the rate floor
- Optional extra monthly payments and lump sums, and when they start
When to use it
- Choosing between a fixed-rate loan and an ARM
- Seeing the highest payment the ARM caps allow
- Testing how extra principal changes either loan
Why it matters
An ARM at today's start rate may look attractive — until you model what a rate adjustment does to the payment. Showing this scenario protects clients and makes the advisor look thorough, not salesy.
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