An adjustable-rate mortgage (ARM) is a type of mortgage loan where the interest rate fluctuates periodically based on changes in a specified financial index, such as the London Interbank Offered Rate (LIBOR) or the U.S. Treasury Bill rate. The interest rate on an ARM is typically fixed for an initial period, after which it adjusts at predetermined intervals according to the terms of the loan agreement. Here are some key characteristics of adjustable-rate mortgages:

  1. Initial Fixed Rate Period: Most ARMs start with an initial fixed-rate period, during which the interest rate remains constant. This period can range from one month to several years, such as 3, 5, 7, or 10 years. After the initial fixed-rate period ends, the interest rate adjusts periodically.

  2. Adjustment Period: After the initial fixed-rate period, the interest rate on an ARM typically adjusts at regular intervals. Common adjustment periods include annually (one year), biennially (every two years), or triennially (every three years), depending on the terms of the loan.

  3. Index and Margin: The interest rate adjustment is tied to a specific financial index, such as the LIBOR or the Treasury rate. Lenders add a margin (a predetermined percentage) to the index rate to determine the new interest rate. The margin remains constant throughout the life of the loan, while the index rate fluctuates based on market conditions.

  4. Interest Rate Caps: ARMs often include interest rate caps to limit how much the interest rate can increase or decrease at each adjustment period and over the life of the loan. Common caps include periodic adjustment caps (limits on how much the interest rate can change at each adjustment) and lifetime caps (limits on the maximum interest rate increase over the entire loan term).

  5. Payment Changes: When the interest rate adjusts, the borrower’s monthly mortgage payment may also change. If the interest rate increases, the monthly payment typically increases, and if the interest rate decreases, the monthly payment may decrease. However, some ARMs have provisions to limit payment changes to prevent payment shock for borrowers.

  6. Risk and Uncertainty: ARMs carry the risk of interest rate fluctuations, which can lead to unpredictable changes in monthly mortgage payments. Borrowers should carefully consider their ability to handle potential payment increases when choosing an ARM.

  7. Potential Cost Savings: In some cases, ARMs may offer lower initial interest rates compared to fixed-rate mortgages, which can result in lower initial monthly payments and potentially save borrowers money, especially if they plan to sell or refinance before the end of the initial fixed-rate period.

Overall, adjustable-rate mortgages can be suitable for borrowers who are comfortable with the potential for payment fluctuations and anticipate changes in their financial situation. However, borrowers should carefully review the terms of the loan, including interest rate caps and adjustment periods, to understand the potential risks and benefits of an ARM compared to a fixed-rate mortgage.