Fixed-Rate vs. Adjustable-Rate Mortgage
October 24, 2026
A fixed-rate mortgage keeps the same interest rate for the life of the loan, so your principal-and-interest payment never changes. An adjustable-rate mortgage (ARM) has an initial fixed period, after which the rate adjusts on a set schedule based on a market index plus a margin, within limits called caps. An ARM can make sense if you expect to sell or refinance before the fixed period ends, while a fixed rate offers long-term predictability.
How an ARM works. ARMs are usually described by their initial fixed period and how often the rate adjusts afterward. When an adjustment happens, the new rate equals the index, which today is commonly based on SOFR (the Secured Overnight Financing Rate), plus the margin set in your loan documents. Caps limit how much the rate can change at the first adjustment, at each later adjustment, and over the life of the loan. On a Loan Estimate, page 1 shows whether the interest rate and payment can increase after closing, and page 2 includes an Adjustable Interest Rate table with the index, margin, caps and adjustment timing. Lenders must also give you the CFPB's Consumer Handbook on Adjustable-Rate Mortgages, often called the CHARM booklet.
Trade-offs to weigh. A fixed rate protects you if rates rise and makes budgeting simple, but you'd need to refinance to benefit if rates fall. An ARM's initial rate is often set below a comparable fixed rate, though that isn't true in every market, and after the fixed period your payment could rise significantly. Ask yourself how long you're likely to keep the loan, whether you could handle the payment at the maximum rate the caps allow, and how you'd feel about that uncertainty. Under the federal ability-to-repay rule, lenders must generally qualify you for an ARM using the maximum rate that could apply in the first several years, which helps, but your own stress test matters too. Our post on interest rate vs. APR explains why the APR on an ARM relies on assumptions about future rates.
What to ask and quick answers. Ask: What is the initial fixed period? What index and margin apply? What are the initial, periodic and lifetime caps? What is the highest possible rate and payment, and when could I reach it? Is there a prepayment penalty? Can I convert to a fixed rate? Compare a fixed and an ARM Loan Estimate for the same loan on the same day, including the In 5 Years totals. Is an ARM risky? It carries rate risk after the fixed period, which caps limit but don't remove. Can you refinance out of an ARM? Usually, if you qualify when the time comes, but that isn't certain. Which is more common? Most borrowers choose fixed rates, but ARMs can fit specific plans.
A fixed-rate mortgage keeps your rate unchanged for the life of the loan. An ARM starts with a fixed period, then adjusts based on an index plus a margin within caps. Choose based on how long you'll keep the loan and whether you could handle the maximum payment, and compare both on same-day Loan Estimates. Sources: CFPB Consumer Handbook on Adjustable-Rate Mortgages; 12 CFR 1026.37(j) and 1026.43(c)(5). General education only. LoFi Rate is an independent matching service, not a lender or mortgage broker. If you request a match, your information is shared with independent mortgage professionals licensed in your state.