Guide · United States
Fixed vs. Adjustable Rate Mortgages (ARMs): Which Is Best?
Last updated 2026-06-27 · Published 2026-06-27
Compare fixed-rate and adjustable-rate mortgages (ARMs) in the US. Learn how interest rate caps work, when an ARM is a smart choice, and the risks involved.
Fixed-Rate Mortgages: Predictability and Stability
A fixed-rate mortgage has an interest rate that remains constant for the entire life of the loan. Whether you choose a 15-year or 30-year fixed loan, your monthly principal and interest payment will never change.
This stability makes budgeting easy and protects you from rising interest rates. It is the most popular choice for buyers who plan to stay in their homes for the long term.
Adjustable-Rate Mortgages (ARMs): Lower Introductory Rates
An adjustable-rate mortgage (ARM) starts with a lower initial interest rate than a comparable fixed-rate mortgage. This initial rate is locked for a set period (usually 5, 7, or 10 years).
After the initial period ends, the interest rate adjusts periodically based on a financial index. If market rates rise, your interest rate and monthly payment will increase. If rates drop, your payment may decrease.
Understanding ARM Rate Caps
To protect borrowers, ARMs include interest rate caps that limit how much your rate can increase. These caps are usually structured as three numbers (e.g., 2/2/5).
The first number is the initial adjustment cap (the maximum rate increase at the first adjustment date). The second number is the periodic adjustment cap (the maximum increase at each subsequent adjustment). The third number is the lifetime cap (the absolute maximum rate increase over the life of the loan).
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Go to calculator →Frequently asked questions
When is an ARM better than a fixed-rate mortgage?
An ARM can be better if you plan to sell the home or refinance the mortgage before the introductory period ends. This allows you to benefit from the lower initial rate without risking future rate adjustments.
What index is used to determine ARM adjustments?
Most modern ARMs use the Secured Overnight Financing Rate (SOFR) or the London Interbank Offered Rate (LIBOR, which is being phased out) as their index, adding a set margin (like 2%) on top.
Educational content only—not mortgage, tax, or legal advice. Confirm any decision with a licensed professional in your jurisdiction.