Adjustable-Rate Mortgages (ARMs) Explained: A Complete Guide for Texas Homebuyers

When many people hear the words adjustable-rate mortgage (ARM), they immediately assume they’re risky. That’s understandable—ARMs were frequently mentioned during the housing crisis nearly two decades ago. However, today’s adjustable-rate mortgages are very different from many of the loan products available before 2008.

In reality, an ARM can be an excellent financing tool when it matches a borrower’s financial goals and expected time in the home.

As a Texas-licensed mortgage professional with more than 27 years of experience, I spend a lot of time helping borrowers compare fixed-rate loans with adjustable-rate mortgages. For some buyers, a fixed rate is absolutely the right answer. For others, an ARM can save thousands of dollars while still fitting their long-term plans.

Here’s everything you should know.

What Is an Adjustable-Rate Mortgage?

An adjustable-rate mortgage (ARM) is a home loan that begins with a fixed interest rate for a predetermined period of time. After that initial fixed period ends, the interest rate may adjust periodically based on current market conditions.

Unlike a fixed-rate mortgage—which keeps the same interest rate for the life of the loan—an ARM has two phases:

• Initial Fixed-Rate Period — your rate and payment stay the same.
• Adjustment Period — your rate can move up or down at set intervals.

During the initial period, your payment remains stable because your interest rate does not change. Once that period expires, the rate adjusts according to a published financial index plus a fixed margin established when your loan closes.

Common ARM Types

The numbers used to describe an ARM tell you two important things:

• The first number indicates how many years the interest rate remains fixed.
• The second number indicates how often the rate adjusts after that (in months).

ARM Type	Fixed Period	Adjusts Every
3/6 ARM	3 years	6 months
5/6 ARM	5 years	6 months
7/6 ARM	7 years	6 months
10/6 ARM	10 years	6 months

Today, most conventional ARMs adjust every six months after the fixed period (a “/6” ARM), although some legacy loans—often still called 5/1 or 7/1 ARMs—adjust annually.

How an ARM Interest Rate Is Calculated

Once your fixed period ends, your lender calculates your new rate using a simple formula:

Current Index + Margin = New Interest Rate

For example:

• Current Index: 3.50%
• Loan Margin: 2.75%
• New Interest Rate: 3.50% + 2.75% = 6.25%

The margin never changes during the life of the loan. Only the index moves.

What Is the Index?

The index is an independently published interest rate that reflects current financial markets. Most modern conventional ARMs use the Secured Overnight Financing Rate (SOFR). SOFR replaced LIBOR and has become the industry standard because it reflects actual overnight borrowing costs in U.S. Treasury markets.

If SOFR rises, ARM rates generally increase. If SOFR falls, ARM rates may decrease. This means an ARM has the potential to move both upward and downward over time—subject to the caps and floor discussed below.

Understanding Rate Caps (and Floors)

One of the biggest misconceptions about ARMs is that the payment can suddenly double overnight. Today’s ARMs include important consumer protections known as interest rate caps. Most conventional ARMs use three caps, typically expressed as a set of numbers like 2/1/5:

Initial Adjustment Cap

Limits how much the rate can increase at the first adjustment. Example: 2%.

If your starting rate was 5.50%, the highest possible rate at the first adjustment would be 7.50%—even if market rates increased more than that.

Periodic Adjustment Cap

Limits how much each future adjustment can move, up or down, from the prior rate. Example: 1% or 2%. This prevents dramatic payment swings between adjustment periods. If the newly calculated rate (index + margin) falls within that range, the full calculated rate applies—the cap only kicks in when the calculated rate would otherwise exceed it.

Lifetime Cap

Sets the maximum interest rate your loan can ever reach. For example, a starting rate of 5.50% with a 5% lifetime cap means a maximum possible rate of 10.50%—no matter how high market rates rise.

Many conventional ARMs also include a floor, which sets the lowest the rate can ever go (often equal to the loan’s margin). Your loan documents will specify the exact floor, if any.

Example of How an ARM Changes

Suppose you obtain a 7/6 ARM with these terms:

• Interest Rate: 5.25%
• Margin: 2.75%
• Rate Caps: 2/1/5

That means: fixed for seven years, first adjustment limited to 2%, future adjustments limited to 1% each, and a lifetime increase limited to 5%.

Years 1–7: Interest rate stays at 5.25%.

Year 7 (first adjustment): Market rates have risen and the calculated rate (index + margin) comes to 7.80%. The 2% initial cap only allows the rate to rise to 5.25% + 2% = 7.25%, so your new rate is capped at 7.25%, even though the market-calculated rate was higher.

Six months later (second adjustment): The calculated rate comes to 7.90%. The 1% periodic cap means this adjustment can’t exceed 7.25% + 1% = 8.25%. Since 7.90% is below that 8.25% ceiling, the cap doesn’t need to limit anything—your new rate becomes the full calculated rate of 7.90%.

If rates later fall, your rate may also decrease at future adjustments, subject to any applicable floor and the periodic cap.

How Lenders Qualify Borrowers for an ARM

Because rates can rise after the fixed period, many loan programs require you to qualify at a higher “qualifying rate” rather than the initial low ARM rate—particularly for ARMs with a fixed period shorter than five years. Depending on the loan program, that may mean qualifying at the fully indexed rate (index + margin) or the note rate plus a set number of percentage points. This protects you from being approved for a payment you couldn’t afford once the rate adjusts. Ask your loan officer exactly how your specific ARM program will qualify you before you commit.

Why Would Someone Choose an ARM?

Many buyers never keep the same mortgage for 30 years. Some move. Some refinance. Some pay the loan off early. Some receive promotions or expect significant income growth.

If you expect to own the home for fewer years than the fixed period of the ARM, you may never experience an adjustment. Examples include:

• Military families expecting relocation
• Medical residents
• Corporate transfers
• Growing families planning to move
• First-time buyers expecting to upgrade
• Investors planning to sell
• Buyers expecting to refinance after improving credit

Advantages of an ARM

Lower Initial Interest Rate. ARMs often start with a lower rate than comparable fixed-rate mortgages, which can reduce your monthly payment during the fixed period.

Increased Purchasing Power. Lower payments may allow buyers to qualify for a slightly higher-priced home while remaining within underwriting guidelines.

Potential Savings. If you sell or refinance before the first adjustment, you may save thousands in interest compared with choosing a higher fixed rate.

Rates Can Decrease. Unlike a fixed-rate loan, ARM rates can move lower if market indexes decline.

Risks of an ARM

An ARM isn’t the right choice for everyone. Potential drawbacks include:

• Monthly payments may increase after the fixed period.
• Budgeting becomes less predictable over time.
• Rising market rates may increase total interest costs.
• Borrowers planning to stay long-term may ultimately pay more than they would have with a fixed-rate mortgage.

Fixed Rate vs. ARM

A Fixed Rate May Be Better If:

• You plan to stay in the home for many years.
• You prefer predictable monthly payments.
• You want protection from future rate increases.
• Your budget has limited flexibility.

An ARM May Be Better If:

• You expect to move before the first adjustment.
• You anticipate refinancing.
• You want lower initial payments.
• You have a clear financial strategy that aligns with the ARM’s fixed period.

Common ARM Myths

Myth: “My payment can double overnight.”
False. Rate caps limit how quickly the interest rate can increase, both at the first adjustment and at every adjustment after that.

Myth: “ARMs are only for risky borrowers.”
False. Many borrowers with excellent credit intentionally choose ARMs because they fit their financial goals and expected time in the home.

Myth: “The lender decides my new rate.”
False. The lender doesn’t set your new rate at their discretion—it’s calculated using the published index plus the margin established in your loan documents.

Myth: “ARMs always become more expensive.”
False. If the underlying index declines, your interest rate may decrease at future adjustment dates, subject to any minimum rate (floor) specified in your loan documents.

Questions to Ask Before Choosing an ARM

Before selecting any adjustable-rate mortgage, ask your lender:

1. What index does this loan use?
2. What is the margin?
3. What are the initial, periodic, and lifetime caps—and is there a floor?
4. How often does the rate adjust?
5. What is the maximum possible payment?
6. How will I be qualified—at the start rate or a higher qualifying rate?
7. How long do I realistically expect to own this home?
8. Would refinancing before the adjustment period likely make sense if market conditions change?

Understanding these details helps you make an informed decision rather than simply focusing on the initial interest rate.

The Bottom Line

An adjustable-rate mortgage isn’t inherently good or bad—it is simply a financing tool. Like any financial product, its value depends on how well it matches your goals.

For buyers who expect to move, refinance, or pay off their loan before the adjustment period begins, an ARM can provide meaningful savings through a lower initial interest rate. For those planning to stay in their home for decades and who value long-term payment stability, a fixed-rate mortgage may be the better fit.

The key is understanding how the loan works before you commit. A well-structured ARM should never come as a surprise years down the road. You should know exactly when your rate may adjust, how it’s calculated, what limits apply, and how those changes could affect your monthly payment.

Every borrower’s situation is different, which is why comparing multiple loan options is one of the most valuable parts of the mortgage process.

Homewood Mortgage, LLC | NMLS #294974 | Wayne Wallace NMLS #745186 | Licensed in Texas | This is not a commitment to lend. Rates, margins, caps, and dollar figures used throughout this article are illustrative examples only, not a quote. Contact Wayne directly at 945-300-4644 for current rates and terms specific to your situation.