✍️ FinZelo Editorial Team 📅 September 2026 ⏱️ 7 min read
📌 Key Takeaway: A fixed-rate mortgage locks your rate for the life of the loan; an ARM starts with a lower introductory rate that adjusts periodically after the fixed period ends. ARMs make the most sense when you're confident you'll sell or refinance before the first adjustment.

How Fixed-Rate Mortgages Work

Your interest rate and principal-and-interest payment stay the same for the entire loan term, whether that's 15, 20, or 30 years. This predictability is why the vast majority of U.S. homebuyers choose fixed-rate loans.

How ARMs Work

A 5/1 ARM, for example, has a fixed rate for the first 5 years, then adjusts annually based on a market index plus a lender margin, usually with caps limiting how much it can move per adjustment and over the loan's life.

When an ARM Can Make Sense

  • You're confident you'll sell or refinance within the initial fixed period.
  • The ARM's introductory rate is meaningfully lower than available fixed rates.
  • You have enough income flexibility to absorb a potential rate increase later.

When to Stick With Fixed

If you plan to stay in the home long-term, value payment predictability, or current ARM introductory rates aren't meaningfully lower than fixed rates, a fixed-rate loan is almost always the safer choice.

This page is for educational purposes and isn't personalized financial or tax advice. Figures, rates, and program details change frequently — confirm current terms directly with lenders, tax professionals, or the IRS before acting.