Adjustable-Rate Mortgage

What is an Adjustable-Rate Mortgage ?

An adjustable-rate mortgage (ARM) is a type of home loan where the interest rate can change periodically, usually in response to changes in a specified financial index. Unlike a fixed-rate mortgage, where the interest rate remains constant for the entire loan term, an ARM typically has an initial fixed-rate period followed by periodic adjustments.

The initial fixed-rate period, often ranging from one to ten years, provides borrowers with a stable interest rate, allowing them to plan and budget with greater certainty during this time. After the initial period, the interest rate may adjust at predetermined intervals, such as annually. The adjustment is based on changes in an underlying financial index, which is commonly tied to market interest rates.

Adjustable-rate mortgages are characterized by two key components: the index and the margin. The index reflects changes in market interest rates, such as the London Interbank Offered Rate (LIBOR) or the U.S. Treasury Bill rate. The margin is a fixed percentage added to the index to determine the new interest rate. For example, if the index is 3% and the margin is 2%, the borrower's interest rate would be 5%.

How Does an Adjustable Rate Mortgage Work ?

An adjustable-rate mortgage (ARM) works by featuring an interest rate that can fluctuate over time based on changes in a specified financial index. The key components that determine how an ARM functions are the index, margin, initial fixed-rate period, adjustment periods, and associated caps.

1) Index: The interest rate on an ARM is tied to a specific financial index, such as the London Interbank Offered Rate (LIBOR) or the U.S. Treasury Bill rate. The movement of this index reflects changes in the broader financial market.

2) Margin: Lenders add a fixed percentage, known as the margin, to the chosen index to determine the borrower's interest rate. For example, if the selected index is 3% and the margin is 2%, the borrower's interest rate would be 5%.

3) Initial Fixed-Rate Period: ARMs typically begin with an initial fixed-rate period during which the interest rate remains constant. This period can vary, commonly ranging from one to ten years, providing borrowers with a predictable and stable payment environment initially.

4) Adjustment Periods: After the initial fixed-rate period, the ARM enters the adjustable phase, where the interest rate can change. The adjustment periods specify how often these changes occur, with common intervals being one year, three years, or five years.

5) Caps: To protect borrowers from sharp increases in interest rates, ARMs often have caps. There are two types of caps:
  • Periodic Adjustment Caps: Limit the amount by which the interest rate can change during a single adjustment period.
  • Lifetime Caps: Restrict the total cumulative increase over the entire life of the loan.

Here's a simplified example to illustrate how an ARM works: Let's say you have a 5/1 ARM with a 3% initial interest rate, a 2% margin, and a 1-year adjustment period. After the initial 5-year fixed-rate period, the interest rate could adjust annually based on changes in the specified index, subject to any caps in place.

While ARMs offer the potential for lower initial interest rates compared to fixed-rate mortgages, they also carry the risk of rate increases in the future. The periodic adjustments can lead to changes in monthly mortgage payments, making budgeting more challenging for homeowners. To mitigate this risk, ARMs often come with interest rate caps, which limit how much the rate can increase during each adjustment period and over the life of the loan.

Types of Adjustable-Rate Mortgage

There are several types of adjustable-rate mortgages (ARMs), each with its own characteristics and structure. The most common types include:

1) Hybrid ARMs:
  • 5/1 ARM: This is one of the most common hybrids. The "5" indicates the initial fixed period of five years, during which the interest rate remains constant. After this period, the rate adjusts annually.
  • 7/1 ARM, 10/1 ARM: Similar to the 5/1 ARM, these hybrids have initial fixed-rate periods of seven or ten years, respectively, before transitioning to annual adjustments.

2) Interest-Only ARMs:
With interest-only ARMs, borrowers only pay interest on the loan during the initial fixed-rate period, usually five or ten years. Afterward, both principal and interest payments are required, and the interest rate can adjust periodically.

3) Option ARMs (Adjustable-Rate Mortgages):
Option ARMs provide borrowers with multiple payment options during the initial fixed-rate period. These options may include making minimum payments, interest-only payments, or fully amortizing payments. However, making minimum payments can lead to negative amortization, where the loan balance increases over time.

4) Payment-Option ARMs:
Similar to option ARMs, payment-option ARMs offer flexibility in choosing different payment options. Borrowers can select from various payment methods, such as interest-only, fully amortizing, or a minimum payment that may not cover the interest, leading to potential negative amortization.

5) Cash Flow ARM:
This type of ARM is designed to provide more flexibility for borrowers, particularly those with irregular income. It allows for varying payment amounts and frequency, depending on the borrower's cash flow.

6) Convertible ARMs:
Convertible ARMs give borrowers the option to convert the adjustable-rate loan into a fixed-rate mortgage at specific points during the loan term. This provides a degree of protection against rising interest rates.

7) Libor ARMs:
Some ARMs are specifically tied to the London Interbank Offered Rate (LIBOR) as the index. Given changes in the financial landscape, it's important to note that the use of LIBOR has decreased, and many financial institutions are transitioning to alternative benchmark rates.

Adjustable-Rate Mortgage Requirements

1) Creditworthiness: Applicants with a good to excellent credit score (usually 620 or higher) are generally eligible for ARMs.

2) Stable Income: Lenders prefer borrowers with a stable and verifiable income source, demonstrating the ability to make mortgage payments.

3) Debt-to-Income Ratio: Lenders assess the debt-to-income ratio, typically favoring applicants with a lower ratio, ensuring they can manage additional debt.

4) Documentation: Eligible individuals must provide comprehensive documentation, including proof of income, employment verification, tax returns, and details about assets and debts.

5) Financial Stability: Borrowers with a history of financial stability and responsible financial management are more likely to qualify for ARMs.

6) Pre-Approval: While not mandatory, obtaining pre-approval can strengthen eligibility by demonstrating financial credibility to lenders.

7) Capacity for Rate Changes: Borrowers should assess their capacity to handle potential interest rate adjustments, considering potential fluctuations in monthly payments.

8) Closing Costs and Fees: Individuals should be prepared to cover closing costs and fees associated with the mortgage process.

It's important to note that eligibility criteria may vary among lenders, and meeting these requirements doesn't guarantee approval. Prospective borrowers should consult with lenders to determine their specific eligibility and explore available mortgage options.

How to Get Adjustable-Rate Mortgage ?

To get an Adjustable-Rate Mortgage (ARM), you'll typically need to follow a process similar to that of obtaining any other type of mortgage. Here are the general steps:

1) Assess Your Financial Situation:
Evaluate your financial health, including your income, expenses, credit score, and debt-to-income ratio. This will help you determine how much you can afford and what type of mortgage suits your needs.

2) Research and Compare Lenders:
Research different lenders, including banks, credit unions, and mortgage brokers. Compare their offerings, interest rates, terms, and customer reviews to find a lender that fits your requirements.

3) Understand ARM Terms:
Familiarize yourself with the terms associated with ARMs, such as the initial fixed-rate period, index, margin, adjustment frequency, and caps. This knowledge will help you make an informed decision.

4) Gather Documentation:
Prepare the necessary documents, including proof of income, employment verification, tax returns, and information about your assets and debts. Lenders will use this information to assess your eligibility for a mortgage.

5) Get Pre-Approved:
Consider getting pre-approved for a mortgage. This involves submitting your financial information to a lender, who will then provide a pre-approval letter indicating the amount you may be eligible to borrow.

6) Choose Your Loan:
Select the specific ARM product that aligns with your financial goals. Decide on the initial fixed-rate period, the index used for adjustments, and other terms that suit your needs.

7) Submit the Application:
Complete the mortgage application with your chosen lender. Be prepared to provide detailed information about your financial situation. The lender will review your application and may request additional documentation.

8) Lock in Your Rate:
If you're satisfied with the current interest rate, you may choose to lock it in. This action guarantees that the rate will remain the same during a specified period, typically until the loan closes.

9) Wait for Approval:
The lender will review your application, verify the provided information, and assess your creditworthiness. The underwriting process may take some time.

10) Close the Loan:
Once your mortgage is approved, you'll attend the closing, where you'll sign the necessary documents. This includes the ARM agreement outlining the terms and conditions of your loan.

11) Monitor Market Conditions:
Keep an eye on economic and market conditions, especially if you choose an ARM. Understand how changes in interest rates might impact your future payments.

Borrowers considering an ARM should carefully review the loan terms, especially the caps, to understand the potential fluctuations in their monthly mortgage payments. The decision to choose an ARM over a fixed-rate mortgage often depends on factors such as the borrower's risk tolerance, financial goals, and how long they intend to stay in the home. It's crucial to work closely with your chosen lender and seek professional advice if needed.

Adjustable Rate Mortgage Example

Let's consider an example of an Adjustable-Rate Mortgage (ARM) to illustrate how it works:

  • Loan Amount: $200,000
  • Initial Fixed-Rate Period: 5/1 ARM
  • Initial Interest Rate: 3%
  • Index: One-Year Treasury Constant Maturity (TCM)
  • Margin: 2%
  • Adjustment Period: Annually
  • Caps: 2% annual adjustment cap, 6% lifetime cap


1) Year 1-5 (Initial Fixed-Rate Period):
Borrower enjoys a fixed interest rate of 3% for the first five years, resulting in consistent monthly payments.

2) Year 6 (First Adjustment):
The initial fixed-rate period ends, and the interest rate adjusts based on the performance of the chosen index. Suppose the index increased by 1% during this period. The new interest rate would be 3% (initial rate) + 1% (index change) + 2% (margin) = 6%.

3) Year 7 (Second Adjustment):
If the index remains stable, there is no change to the interest rate. However, if the index increases by 2%, the interest rate can adjust, subject to the 2% annual cap. Therefore, the maximum interest rate for this year would be 6% (previous year's rate) + 2% (annual cap) = 8%.

4) Year 8 (Third Adjustment):
Suppose the index decreases by 1%. The interest rate can adjust, but it cannot fall below the initial rate of 3%. Therefore, the new interest rate would be 3% (initial rate) - 1% (index change) + 2% (margin) = 4%.

5) Year 9 (Fourth Adjustment):
If the index remains unchanged, the interest rate stays at 4%.

6) Year 10 (Fifth Adjustment):
Suppose the index increases by 3%. The interest rate can adjust, but it cannot exceed the lifetime cap. Therefore, the maximum interest rate for this year would be 4% (previous year's rate) + 3% (index change) + 2% (margin) = 9%. However, the lifetime cap is 6%, so the interest rate will be capped at 6%.

The borrower experienced fluctuations in the interest rate after the initial fixed-rate period, depending on changes in the chosen index. The caps in place provided some protection against drastic increases in the interest rate, contributing to a degree of predictability in the mortgage payments.

How to Calculate Adjustable-Rate Mortgage Cost ?

Calculating the cost of an ARM involves considering several factors, including the initial loan amount, interest rate, adjustment caps, and the expected interest rate changes. Here are the basic steps:

1) Determine the Initial Loan Amount:
Identify the amount you are borrowing, which is the initial loan amount.

2) Understand the Initial Interest Rate:
Know the initial interest rate of the ARM, which is the rate during the fixed-rate period.

3) Calculate Monthly Payments during Fixed-Rate Period:
Use the loan amount, initial interest rate, and loan term to calculate the monthly payments during the fixed-rate period using a mortgage payment calculator.

4) Estimate Future Interest Rates:
Consider possible future interest rate scenarios based on economic forecasts, market conditions, and the chosen index.

5) Predict Adjusted Interest Rates:
Estimate how the interest rate may change during adjustment periods. Be aware of caps that limit the maximum increase in a single period and over the life of the loan. For each adjustment period, calculate the adjusted interest rate by adding the current index value to the margin.

Adjusted Rate = Index Rate + Margin

6) Calculate Future Monthly Payments:
Use the estimated adjusted interest rates to calculate future monthly payments during the adjustable phase of the ARM.

7) Consider Potential Negative Amortization:
If your ARM has an option for negative amortization, consider the impact on the loan balance and the potential increase in the overall cost.

8) Factor in Closing Costs:
Account for any closing costs associated with the ARM, including origination fees, application fees, and other charges.

9) Evaluate the Lifetime Cost:
Consider the potential lifetime cost of the ARM, taking into account all expected adjustments and caps, to understand the total cost over the loan term.

Pros of Adjustable-Rate Mortgage

1) Lower Initial Interest Rates: ARMs often start with lower interest rates than fixed-rate mortgages, resulting in lower initial monthly payments.

2) Potential for Initial Savings: If interest rates remain stable or decrease, borrowers may benefit from lower overall interest costs during the initial fixed-rate period.

3) Short-Term Ownership Benefits: ARMs can be advantageous for those planning to sell or refinance within the initial fixed-rate period, offering cost savings during that time.

4) Interest Rate Caps: Many ARMs come with interest rate caps, limiting how much the interest rate can increase at each adjustment, providing a degree of protection against significant rate hikes.

5) Convertible Options: Some ARMs offer conversion features, allowing borrowers to convert to a fixed-rate mortgage if they become concerned about future interest rate fluctuations.

Cons of Adjustable-Rate Mortgage

1) Interest Rate Risk: The primary disadvantage is the uncertainty of future interest rate increases, potentially leading to higher monthly payments and increased overall borrowing costs.

2) Budgeting Challenges: Monthly payments can fluctuate, making it difficult for borrowers to budget and plan for future expenses.

3) Payment Shock: During an interest rate adjustment, borrowers may face a significant increase in their monthly payments, potentially causing financial strain.

4) Potential for Negative Amortization: Certain ARMs, especially those with option features, carry the risk of negative amortization, where the loan balance may increase if minimum payments don't cover the interest.

5) Long-Term Cost Uncertainty: While ARMs may offer initial cost savings, the long-term cost is uncertain and depends on future interest rate movements, making financial planning more challenging.


Q: How does the interest rate on an ARM change?
A: The interest rate on an ARM can change based on fluctuations in a chosen financial index, such as LIBOR or the U.S. Treasury Bill rate. The rate is typically recalculated at specified intervals after the initial fixed-rate period.

Q: Who offers adjustable rate mortgage?
A: Adjustable-rate mortgages (ARMs) are commonly offered by various financial institutions, including banks, credit unions, and mortgage lenders, providing borrowers with options to choose from based on their preferences and financial needs.

Q: What is the initial fixed-rate period in an ARM?
A: The initial fixed-rate period is a set period at the beginning of the ARM during which the interest rate remains constant. This period, often ranging from one to ten years, provides borrowers with predictable monthly payments.

Q: Are there limits to how much the interest rate can change in an ARM?
A: Yes, many ARMs have interest rate caps that limit how much the interest rate can increase during a specific adjustment period and over the life of the loan. This provides borrowers with some protection against drastic rate hikes.

Q: What factors should borrowers consider when choosing an ARM?
A: Borrowers should consider their financial goals, risk tolerance, and how long they plan to stay in the home. Understanding the terms of the ARM, including the index, margin, caps, and adjustment frequency, is crucial for making an informed decision.

Q: Can I convert my ARM to a fixed-rate mortgage?
A: Some ARMs offer conversion options that allow borrowers to convert to a fixed-rate mortgage at specific points during the loan term. This can provide a level of stability if the borrower becomes concerned about future interest rate fluctuations.

Q: What is payment shock in the context of ARMs?
A: Payment shock refers to the significant increase in monthly mortgage payments that borrowers may experience during an interest rate adjustment. It is a potential risk associated with ARMs, and borrowers should be prepared for possible fluctuations in their payment amounts.

Q: How does negative amortization work with certain ARMs?
A: Negative amortization can occur when the minimum payments on an ARM do not cover the full amount of interest owed. The unpaid interest is added to the loan balance, leading to an increase in the overall debt over time. Borrowers should carefully review loan terms to understand the potential for negative amortization.