An adjustable-rate mortgage, or ARM, is a home loan whose interest rate is fixed for an initial period and then changes at set intervals based on a benchmark. During the intro period the rate is often lower than a comparable fixed-rate loan, which keeps early payments down. After that, the rate can move up or down, so your payment can change. The appeal is the lower start; the catch is the uncertainty later. This is general information, not personalized financial advice; verify any mortgage decision with a qualified lender and your own numbers.
How an ARM works
ARMs are labelled with two numbers, like 5/1 or 7/6. The first number is how many years the rate stays fixed. The second describes how often it adjusts after that, for example yearly or every six months. When it adjusts, the new rate is tied to a published index plus a fixed margin set by the lender.
Crucially, ARMs come with caps that limit how far the rate can move: a cap on the first adjustment, a cap on each later adjustment, and a lifetime cap. These caps are the guardrails, so read them carefully before signing.
ARM vs fixed-rate mortgage
|
Adjustable-rate (ARM) |
Fixed-rate |
| Intro rate |
Often lower |
Set for the whole term |
| After intro period |
Can rise or fall |
Never changes |
| Payment certainty |
Lower |
High |
| Best for |
Shorter expected stay |
Long-term certainty |
| Main risk |
Higher payments later |
Paying more if rates fall and you do not refinance |
The decision rule is simple. If you are confident you will sell or refinance before the fixed period ends, the lower intro rate of an ARM can save money. If you plan to stay for the long haul and need predictable payments, a fixed rate usually wins. To compare loan lengths on the fixed side, see 15 vs 30-year mortgage.
Who it is and is not for
An ARM can fit someone who expects to move within a few years, anticipates rising income, or believes they will refinance before the adjustment hits. The lower early payment frees up cash in the meantime.
It is a poor fit if you need certainty, are stretching to afford the home already, or cannot absorb a higher payment if rates rise. Do not lean on the teaser rate to qualify for a house you could not afford at the post-adjustment rate.
What to skip
- Choosing an ARM only for the low intro rate. If you will stay long-term, the later uncertainty can erase the early savings.
- Ignoring the caps. The first-adjustment, periodic, and lifetime caps define your worst case; know all three.
- Assuming you can always refinance. Refinancing depends on rates, your credit, and home value, none of which are guaranteed.
- Stretching to the maximum. Buy assuming the payment could climb, not just the introductory figure.
FAQ
What does 5/1 ARM mean?
The rate is fixed for five years, then adjusts once a year afterward based on an index plus the lender margin, within the loan caps.
Can my ARM payment go down?
Yes. If the benchmark index falls, your rate and payment can decrease at the next adjustment, subject to the loan terms.
Are ARMs riskier than fixed mortgages?
They carry more payment uncertainty after the fixed period. Whether that risk suits you depends on how long you will stay and your budget cushion.
Should I get an ARM in 2026?
It depends entirely on your timeline, budget, and the rate gap between ARM and fixed at the time. Run your own numbers and verify with a lender.
Where to go next
Compare a 15 vs 30-year mortgage, learn how to get a mortgage, and weigh renting vs a mortgage.