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Key takeaways

  • Adjustable-rate mortgages (ARMs) come with an interest rate that changes at predetermined times, such as once a year. The rate can go up or down depending on economic factors.
  • ARMs typically have a low introductory rate, which translates to more affordable monthly mortgage payments initially.
  • ARMs are generally better for borrowers who plan to stay in the home for a shorter time, or who expect to refinance before the introductory rate period ends.

When you get a mortgage, you can choose a fixed interest rate or one that changes. While fixed-rate mortgages keep the same rate and payment for the life of the loan, adjustable-rate mortgages (ARMs for short) have fluctuating rates that change how much you pay.

What is an adjustable-rate mortgage (ARM)?

Key terms

Adjustable-rate mortgage
An adjustable-rate mortgage, or ARM, is a home loan with an interest rate that fluctuates periodically. This means that the monthly payments can go up or down.

Generally, the initial interest rate on an ARM mortgage is lower than that of a comparable fixed-rate mortgage. After that period ends, interest rates — and your monthly payments — can rise or fall.

Interest rates are unpredictable, though in recent decades they’ve tended to trend up and down over multi-year cycles. Given the recent increase in rates, ARMs can help you save money in the early days of your loan by securing a lower initial rate. Just keep in mind that after the first few years of the loan, the rate — and your monthly payment — might go up.

The initial interest rate on an adjustable-rate mortgage is sometimes called a “teaser” rate, and even ARMs themselves are sometimes referred to as “teaser” loans. While they’re generally one and the same, there can be a difference between a regular ARM and a riskier teaser loan that offers an extremely discounted rate upfront, followed by a dramatic change (usually upward) in the rate.

Fixed-rate vs. adjustable-rate mortgages

The difference between fixed-rate and adjustable-rate mortgages is simple: fixed-rate mortgages have the same rate for the life of the loan, whereas ARMs have a rate that moves up or down after an introductory period. Other than that, they work similarly: You pay them off each month, in payments that include principal and interest and sometimes homeowners insurance and property taxes.

“Choosing an ARM over a fixed-rate mortgage isn’t a clear-cut decision,” says Jeff Ostrowski, principal writer at Bankrate. “Average 5/6 ARM rates were about a quarter-point lower than 30-year fixed-rate loans in Bankrate’s latest survey. On a $400,000 loan, that equates to savings of $67 a month — or about $4,000 over five years. The downside is that if rates are higher in five years, you’ll be on the hook for a higher payment.”

How does an adjustable rate mortgage work?

ARMs are comprised of a few components:

  • Fixed period: This is the period with the low introductory (and fixed) rate, which lasts for three to 10 years, depending on the loan. In an ARMs-naming convention, this is the first number (for instance, the “7” in “7/1”).
  • Adjustable period: The adjustable period starts after the fixed period ends, continuing until you sell, refinance or pay off the loan.
  • Rate of adjustment: ARMs adjust every six months to a year. This is the second number in the name (the “1” in “7/1” or the “6” in “5/6″).

What are ARM rate caps?

ARMs come with rate caps that insulate you from possible steep year-to-year increases in monthly payments. These caps limit the amount by which rates and payments can change.

  • A periodic rate cap: Limits how much the interest rate can change from one year to the next.
  • A lifetime rate cap: Limits how much the interest rate can rise over the life of the loan.
  • A payment cap: Limits the amount the monthly payment can rise over the life of the loan in dollars, rather than how much the rate can change in percentage points.

Types of ARMs

ARMs are generally 30-year mortgages, but they can vary a lot in how often the fixed rate lasts and how often the rates change once you’re into the variable-rate period. Here are the most typical loan terms:

  • 3/6 and 3/1 ARMs: 3/6 and 3/1 ARMs have a fixed introductory rate for the first three years of the mortgage, then switch to an adjustable rate for the remaining 27 years. 3/6 ARMs adjust every six months, whereas 3/1 ARMs adjust yearly.
  • 5/6 and 5/1 ARMs: 5/6 and 5/1 ARMs offer a fixed intro rate for the first five years of the mortgage, then switch to an adjustable rate for the remaining 25 years. 5/6 ARMs adjust every six months, and 5/1 ARMs adjust yearly.
  • 7/6 and 7/1 ARMs: 7/6 and 7/1 ARMs come with a fixed intro rate for the first seven years of the mortgage, then move to an adjustable rate for the remaining 23 years. 7/6 ARMs adjust every six months, and 7/1 ARMs adjust yearly.
  • 10/6 and 10/1 ARMs: 10/6 and 10/1 ARMs have a fixed intro rate for the first 10 years of the mortgage, then move to an adjustable rate for the remaining 20 years. 10/6 ARMs adjust every six months, and 10/1 ARMs adjust yearly.

Along with these common loan terms, there are three main types of ARMs: hybrid, interest-only and payment-option.

Hybrid ARM

A hybrid ARM is the traditional adjustable-rate mortgage. The loan starts with a fixed interest rate for a few years (usually three to 10), and then the rate adjusts up or down on a preset schedule, such as once per year.

Interest-only ARM

Interest-only ARMs are adjustable-rate mortgages in which the borrower only pays interest (no principal) for a set period. Once that interest-only period ends, the borrower starts making full principal and interest payments.

The interest-only period might last a few months to a few years. During that time, the monthly payments will be low (since they’re only interest), but the borrower also won’t build any equity in their home (unless the home appreciates in value).

Payment-option ARM

With a payment-option ARM, borrowers select their own payment structure and schedule, such as interest-only; a 15- 30- or 40-year term; or any other payment equal to or greater than the minimum payment. (The minimum payment is based on a typical 30-year amortization with the initial rate of the loan.)

A payment-option ARM, however, could result in negative amortization, meaning the balance of your loan increases because you aren’t paying enough to cover interest. If the balance rises too much, your lender might recast the loan and require you to make much larger, and potentially unaffordable, payments.

Pros and cons of ARMs

It’s important to weigh the pros and cons of ARMs, which include:

Pros of adjustable-rate mortgages

  • Lower monthly payments at the start. You’ll get a lower initial interest rate, translating to lower monthly payments and the potential to allocate more money toward the principal.
  • More budget flexibility. With a lower monthly payment at the beginning, you could choose to pay more when you have extra cash and less when you need money for other things.

Cons of adjustable-rate mortgages

  • Higher monthly payment after the intro period. Your interest rate and monthly payments might rise, and to an unaffordable level, even with the cap limit.
  • More complex. Unlike a fixed-rate mortgage, this mortgage type involves a more complex structure that could be difficult to understand.

Is an adjustable-rate mortgage right for you?

Adjustable-rate mortgages trade long-term certainty for upfront savings by providing a lower interest rate for the first years of your loan. They’re generally ideal for borrowers who don’t plan to stay in their home long-term or plan to refinance after a few years.

If you’re going to stay in your home for decades, an ARM can be risky — you might find your mortgage payments rising significantly once the fixed-rate period ends. If you’re buying your forever home, think carefully about whether an ARM is right for you. Bankrate’s ARM calculator can help you decide whether this type of loan is the best choice.

Adjustable-rate mortgage FAQ

  • Most ARM rates are tied to the performance of one of three major indexes:

    • Weekly constant maturity yield on one-year Treasury bill: The yield debt securities issued by the U.S. Treasury are paying, as tracked by the Federal Reserve Board
    • 11th District cost of funds index (COFI): The interest financial institutions in the western U.S. are paying on deposits they hold
    • The Secured Overnight Financing rate (SOFR): The SOFR has replaced the London Interbank Offered Rate (LIBOR) as the benchmark rate for ARMs

    Your loan paperwork identifies which index a particular ARM follows.

    To set ARM rates, mortgage lenders take an index rate and add an agreed-upon number of percentage points, called the margin. The index rate can change, but the margin does not.

    For example, if the index is 4.25 percent and the margin is 3 percentage points, they are added together for an interest rate of 7.25 percent. If, a year later, the index is 4.5 percent, then the interest rate on your loan will rise to 7.5 percent.

  • The basic requirements for an ARM loan include a credit score of at least 620 and a debt-to-income ratio (DTI) of 50 percent or less. Further requirements depend on whether you get a conventional, FHA or VA ARM loan.
  • Adjustable-rate mortgages (ARMs) became available to homebuyers in the U.S. in the early 1980s.