ARM vs fixed-rate mortgage: which is the better bet?
· 7 min read
How an ARM is structured
A 5/1 ARM has a 5-year fixed period, then resets annually based on a published index (commonly SOFR) plus a fixed margin. The new rate is capped per adjustment and over the life of the loan, but the lifetime cap is often 5–6 percentage points above your starting rate.
A 7/1 ARM works the same way with a 7-year fixed period.
When an ARM makes sense
- You’re certain to sell or refinance within the fixed period (e.g., job relocation expected, building equity for an upgrade).
- The initial rate discount vs a fixed loan is large — typically 0.75% or more.
- You have the financial cushion to absorb the worst-case reset if plans change.
The hidden risk
Most ARM borrowers underestimate the timing risk of refinancing. If rates rise, refinancing into a new fixed loan after year 5 will be even more expensive than your reset, not less. ARMs carry an embedded option that the lender benefits from; you are short volatility.
Worst-case stress test
Before taking an ARM, run our calculator with the lifetime cap rate. If you couldn’t comfortably make that payment, the ARM is too risky regardless of your current plan.
Frequently asked questions
What is the key takeaway about ARM vs fixed rate mortgage?
An adjustable-rate mortgage offers a lower initial fixed period (typically 5, 7, or 10 years) and then resets annually based on a benchmark rate plus a margin. ARMs are rational only when you have high confidence you will sell or refinance before the reset. If rates are already historically low, the asymmetric risk usually favors a fixed rate.
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