What is an ARM loan? How adjustable-rate mortgages work

An adjustable-rate mortgage, or ARM, locks in a fixed interest rate for only part of the loan's term.

For many borrowers, ARMs offer lower interest rates during this fixed-rate period, when compared to the fixed rate they'd get on a 30-year mortgage.

This creates the potential to save money or to qualify for a bigger loan amount.

But that potential must be balanced with the ARM's unpredictability. After its fixed rate expires, an ARM's rate will change to match market conditions at that time.

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How does an ARM loan work?

You can tell how an ARM works by looking at its numbers. A 5/1 ARM, for example, locks a fixed rate for five years. Then its rate changes once a year. A 7/1 ARM keeps its initial rate for seven years before switching rates annually. And so on.

How much will the ARM's rate change? That depends on two other numbers:

• The index: This is the benchmark interest rate, which changes with market conditions. Most modern ARMs index to the Federal Reserve's standard overnight financing rate, or SOFR.
• Margin: An ARM adds a margin rate to the index rate to arrive at the loan's rate. The margin never changes throughout the life of the loan.

Let's say the current SOFR is 3.75% and the margin is 3%. The ARM's rate would be 6.75%. If the SOFR is 4% when the ARM adjusts its rate, the new rate would be 7% (4% SOFR + 3% margin).

The two phases of an ARM

Simply put, an ARM has two phases: A fixed-rate phase and an adjustable-rate phase.

The initial fixed period provides temporary stability

During the ARM's fixed period — whether five, seven, or 10 years — the loan's interest rate and monthly payment due for principal and interest will not change.

During this initial period, the ARM works like a fixed-rate loan, but often with a lower rate compared to 30-year fixed-rate loans.

The adjustment period refinances the remaining debt

Once the fixed period expires, your rate adjusts annually (or twice a year for some ARMs).

When the first adjustment comes due, the remaining loan balance will automatically refinance into a new rate based on the market conditions at that time.

Many homeowners plan to refinance their homes into a fixed rate loan before their ARM starts to adjust.

ARM rate caps limit how high a rate can climb

Modern ARMs come with built-in rate caps that limit how high the loan's rate can climb.

ARMs include three different rate caps which interact with each other to control how much the rate changes each year.

• The first rate cap controls how high the rate can climb on its first adjustment.
• The second rate cap controls how high the rate can move on all other adjustments.
• The third cap limits the lifetime increase in the ARM's rate.

This table shows a loan with caps set at 2/2/5:

Cap type	What it limits	Example (2/2/5)
Initial adjustment cap	Maximum rate change at the first adjustment	Rate cannot rise more than 2% above initial rate
Periodic adjustment cap	Maximum rate change at each subsequent annual adjustment	Rate cannot move more than 2% per year after that
Lifetime cap	Maximum total rate increase over the loan's life	Rate can never be more than 5% above your starting rate

So, using a 2/2/5 cap structure on a loan that starts at 6% means the rate can never exceed 11% over the life of the loan, can never jump more than 2% in a single year, and cannot rise more than 2% at the first adjustment.

Caps do not prevent your rate from rising. They limit how fast and how far it can go.

Types of ARM loans

Better offers three ARM terms on conventional and jumbo loans. Each suits a slightly different buyer profile.

ARM type	Fixed period	Adjusts every	Best for
5/1 ARM	5 years	1 year	Buyers planning to sell or refi within 5 years
7/1 ARM	7 years	1 year	Buyers with a 5–7 year horizon
10/1 ARM	10 years	1 year	Buyers wanting rate flexibility over a longer fixed window

Jumbo ARM loans follow the same structure but apply to loan amounts above conforming limits, typically homes priced above roughly $800,000.

Because jumbo loans carry larger balances, even a modest rate reduction during the fixed period produces meaningful monthly savings, making the ARM structure particularly attractive to high-value home buyers with a defined exit strategy.

ARM loan pros and cons

An ARM is a tool that some homebuyers can use to save money. Borrowers who succeed with an ARM know how to factor in the risks as well as the rewards.

Pros	Cons
Lower starting interest rate than a fixed mortgage	Rate and payment can rise after the fixed period
Lower initial monthly payment	Harder to budget long-term
Savings are real if you sell or refi before adjustments begin	Rate uncertainty persists for the life of the loan
Can increase buying power on a given budget	Requires a clear exit plan to manage the risk well
Useful in high-rate environments where the spread vs. fixed is wide	If rates rise sharply, caps still allow significant payment increases

Selling or refinancing the home before the ARM's rate adjusts keeps borrowers from ever experiencing a rate adjustment on the ARM.

The risk ARM borrowers take is keeping the loan longer than they expected and experiencing its unpredictability.

If you're not sure about your future plans for moving or refinancing, it's usually best to stick with a 15- or 30-year fixed rate loan, both of which lock in a fixed rate for the life of the loan.

ARM vs. fixed-rate mortgage — which is right for you?

The right choice depends on your unique plans, not on which product is objectively "better." Here is a scenario-based framework:

Situation	ARM or fixed?	Why
You plan to sell or refinance within 5–7 years	ARM	You capture the lower rate and exit before adjustments begin
You plan to stay 10+ years	Fixed	Rate certainty protects you over the long horizon
You are buying a jumbo-priced home and have a clear exit plan	ARM	The rate savings on a large balance are substantial
You are on a tight monthly budget	Fixed	An ARM payment could rise and strain your finances
Rates are elevated and the ARM/fixed spread is wide	ARM	A larger spread means more savings during the fixed period
Rates are low and the ARM/fixed spread is narrow	Fixed	Little benefit to the ARM if the starting rate difference is small

Of course, no data table can contain the nuance of real life for all borrowers. Talk to a loan officer or financial advisor if you'd like to discuss your own unique situation.

And for a more thorough breakdown, see Better's guide to fixed vs. adjustable-rate mortgage loans.

A mortgage pre-approval can help you compare costs on different types of loans.

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FAQ

What is an ARM loan and how does it work?

An ARM loan (adjustable-rate mortgage) is a mortgage with an interest rate that is fixed for an initial period — typically five, seven, or 10 years — and then adjusts once per year based on a market index plus a fixed margin set by your lender.

What does 5/1 ARM mean on a mortgage?

A 5/1 ARM has a fixed interest rate for the first five years of the loan, then adjusts once per year for the remaining loan term. The "5" is the fixed period in years; the "1" is the adjustment frequency in years. A 7/1 ARM fixes for seven years and adjusts annually after that; a 10/1 ARM fixes for 10 years.

What happens to my ARM rate after the fixed period ends?

After the fixed period, your rate is recalculated each year using a market index plus your lender's margin. If the index rises, your rate rises. If it falls, your rate falls. Rate caps limit how much the rate can move. Your lender is required to disclose the cap structure before you close.

What are ARM rate caps and how do they protect me?

ARM caps are contractual limits on rate movement. They are expressed as three numbers, for example, 2/2/5. The first number caps the initial adjustment, the second caps each subsequent annual adjustment, and the third caps the total lifetime increase above your starting rate.

Is an ARM loan a good idea right now?

It depends on your timeline and the current spread between ARM and fixed rates. When the rate difference between an ARM and a comparable fixed loan is significant, the savings during the fixed period are meaningful. ARM borrowers should have an exit plan for the loan in mind before signing the papers.

The bottom line on ARMs

An ARM loan may offer a lower fixed mortgage rate for a while. When the initial rate expires, the ARM's rate will move to match market conditions at that time.

Of course, rates could go down when the ARM adjusts, but most people worry about the possibility of paying more later. This is a real possibility.

The most successful ARM borrowers take advantage of the loan's low starting rate but pay off or refinance before experiencing rate increases.

Is an ARM worth considering? Start with a pre-approval to compare costs.

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