An adjustable-rate mortgage starts with a fixed interest rate for an initial period — commonly 5, 7, or 10 years — then adjusts periodically after that, moving up or down with a benchmark index plus a set margin. A "5/1 ARM" means the rate is fixed for 5 years, then adjusts once per year after that.
Who it's best for
Buyers who know, with real confidence, that they won't be in the home past the fixed-rate period — someone on a 4-year military assignment, a buyer who plans to sell before a known relocation, or someone using the home as a deliberate short-term bridge. It's a much worse fit for anyone uncertain about their timeline.
Why people get an ARM instead of a fixed rate
- Lower initial rate. ARMs typically price below the equivalent 30-year fixed rate during the fixed period, sometimes by a full percentage point or more depending on market conditions.
- Lower payment during the fixed period can mean qualifying for a larger loan amount, or simply more monthly breathing room while the rate is locked.
- Rate caps limit the downside. Most ARMs have caps on how much the rate can move at each adjustment and over the life of the loan, so it's not unlimited risk — but it's still real risk.
What to check before choosing one
Ask for the specific adjustment structure: the index it's tied to, the margin, the initial cap, the periodic cap, and the lifetime cap. Two "5/1 ARMs" from different lenders can have very different worst-case payments depending on those numbers.
ARM structures, caps, and pricing vary significantly by lender and loan program. Review the specific adjustment terms in your Loan Estimate before committing.