ARM vs Fixed-Rate Calculator
Three-scenario ARM math vs fixed baseline. Stops pretending the teaser rate lasts forever.
- 1 Loan amount and term
- 2 Fixed-rate option
- 3 ARM option
- 4 Hold period
- 5 Your results
Tell us about your loan
We need the loan amount and term to run the payment math. Use the balance you'd be financing -- not your home value.
What's the fixed-rate offer?
Get this from your Loan Estimate or a lender quote. If you're comparing hypotheticals, use today's market average -- around 6.5% on a 30-year fixed.
Tell us about the ARM
The teaser rate is locked only during the initial fixed period. After that, it adjusts every 6 months. The caps limit how much it can move at each adjustment.
How long will you keep this loan?
This is the single most important input. If you sell or refi before the fixed period ends, the ARM almost always wins. The longer you stay past that window, the more rate risk you carry.
Your refinance numbers
Here's what the math says. Below that, real lenders compete for your loan if you want quotes.
- Bottom line over your hold
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- ARM best-case total
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- ARM expected-case total
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- ARM worst-case total
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- Fixed-rate total
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Want personalized rate quotes from up to 5 vetted lenders?
Lenders compete for your refi. No credit pull. No upfront fees. Your math above is yours to keep either way.
You're in.
Up to 5 lenders will reach out within 1 business day with their best refi rate for your scenario. No credit pull required for quotes. Reply STOP anytime to opt out. Your math above is yours to keep.
While you wait — read upNumbers above are estimates from standard mortgage math and 2026 program rules. Your actual rate depends on your credit, debt-to-income, property type, and lender pricing. RobotRefi is not a lender and does not originate loans.
How RobotRefi models ARM scenarios
Three scenarios, not one
Best case: rate stays at teaser forever. Expected case: rate drifts up slowly after the fixed period, rising by half the cap at each 6-month adjustment. Worst case: rate jumps straight to the lifetime cap at the first adjustment and stays there.
Month-by-month amortization
At each adjustment the remaining loan balance recasts over the remaining term at the new rate. Totals are the sum of all principal and interest payments during your hold period -- the same cash out of your pocket.
The hold horizon determines everything
If you sell or refinance before the fixed period ends, the ARM almost always wins -- you pay the teaser rate the whole time. The longer you stay past the fixed period, the more the adjustment risk matters. Know your exit plan.