ARM vs. Fixed Rate Mortgage Calculator

ARM vs. fixed rate mortgage: compare your mortgage options

After deciding to purchase a home, you must determine what type of mortgage loan will be most suitable for you; one with fixed monthly payments or payments that may be variable (ARM). It can be confusing to calculate the monthly payments and interest by looking at interest rates, price adjustments, and term lengths. Having a calculator to do the work for you can help you compare your options so that you can make the best decision for your next home purchase.
Your mortgage loan
You have two options for your mortgage loan payments, one where the interest rate is fixed over the length of the loan and the other where the interest rate will vary according to market fluctuations, known as the adjustable rate mortgage (ARM). Within the fixed or variable rate loans you may also be given an option of an interest only mortgage where you do not pay off the capital of the loan within the mortgage period, only the interest, but then you are expected to pay the full principal once the term ends.
How an adjustable rate mortgage works
An adjustable rate mortgage always begins as a fixed rate mortgage for an introductory period, which may last anywhere from three years to ten years, before any yearly rate adjustments take place. For common ARM intervals, please see the table below. The interest rate on the introductory period of a variable mortgage is often lower than a fixed mortgage, making it harder to qualify for this type of loan.
However, once the fixed period ends, the interest rate will adjust annually based on your margin and the performance of a rate index. A margin is a pre-set percentage that will be added on to your selected rate index and will vary by lender, while a rate index is an average rate used by different banks to determine how much they are willing to lend to other financial institutions. There are many rate indexes you may select for your adjustable rate mortgage such as LIBOR, COFI, or MTA.
Common ARM intervals

ARM Type

Months Fixed

10/1 ARM

Fixed for 120 months, adjusts annually for the remaining term of the loan.

7/1 ARM

Fixed for 84 months, adjusts annually for the remaining term of the loan.

5/1 ARM

Fixed for 60 months, adjusts annually for the remaining term of the loan.

3/1 ARM

Fixed for 36 months, adjusts annually for the remaining term of the loan.

Is an adjustable rate mortgage right for me?
An adjustable rate mortgage is most beneficial for homeowners that have an excellent credit score, as most choose this loan for the initial lower payment with the intention to refinance or sell the home within the introductory period. Therefore, if you know the loan you have will be short-lived, it may be worth considering an ARM, but if your future is uncertain, a fixed rate mortgage may be a better option.
What is this calculator for?
The ARM vs. fixed rate mortgage calculator is very simple to use and is designed to help you compare three mortgage payments. It requires precise information about your loan options to provide you with accurate results. It is best to have done some preliminary research on the rates available to you, as rates can vary based on:
• economic conditions
• applicant credit score
• home location
• loan amount
• down payment
• loan term
• loan type
However, if you are unsure of your options, you can make your calculations based on the market averages and return as you consider your budget and learn more about your options.
How to use the calculator
The ARM vs fixed rate mortgage calculator is comprised of two parts: an information section and integrated results. Within the information section is three subsections detailing your loan information, ARM fully amortizing information, and ARM interest only information.
Your loan information
1. Once you can say with certainty how much home you can afford, you may start by adding your mortgage amount to the first line of the calculator.
2. On the second line of the calculator you should select your term in years by using the drop down menu where you may select a term length between 10 and 50 years.
3. Include your expected rate change on the third line of the calculator, which is the annual rate of adjustment of your ARM.
4. On the fourth line of the calculator document the interest rate you are expecting on your fixed rate mortgage loan.
In the next section, you may start to document your variable rate information.
ARM fully amortizing
1. On the fifth line of the calculator add the interest rate on your potential variable mortgage.
2. Next, include the months the rate is fixed for the ARM on the sixth line of the calculator using the common ARM interval table above if needed. During this period the interest rate and the monthly payment will remain unchanged.
3. On the seventh line of the calculator, you can specify the interest rate cap on your adjustable rate mortgage. This is the maximum interest rate for the mortgage that cannot be exceeded.
ARM interest only
The information in this section should be fairly similar to the previous section.
1. Add your interest rate, months rate is fixed, and interest rate cap on the eighth, ninth, and tenth lines of the calculator, referring to the previous subsection if needed.
2. Finally, your amortization report may be provided annually or monthly, depending on your selection here.
Your results
Once this is information is added to the calculator your results will be divided into graphs, tables, and information prompts.
arm vs fixed rate mortgage
Immediately to the right of the data inputs, you will see a smart view of the monthly payments respective to each loan based on the information provided.
arm vs fixed rate
Below the information inputs is a smart prompt of your potential savings with an ARM or interest only ARM.
More comprehensive information about your loan options can be found in the results tabs labelled as your monthly payments, payment schedule, and ARM vs fixed rate mortgage.
arm fixed rate mortgage
Referencing the first results tab you can view a bar graph comparing your monthly payments for each loan option at two points in time: year one and year four. Here you may see a comparison of your fixed rate payments in green, your ARM fully amortizing payments in blue, and your ARM interest only payments in red. If your introductory period is less then four years you may see how the rate adjustments affect either of your ARM payment options.
arm vs fixed rate calculator
The second results tab provides a detailed payment schedule, which summarizes all the monthly payments, respective to each loan option and mortgage balance. Here you can view more clearly how the rate adjustments impact the monthly payments on the mortgage loan to assess and identify when the best time is to refinance your ARM or sell the property.
arm fixed rate calculator
Finally, the third results tab will provide your potential savings on your ARM vs. fixed rate mortgage. Savings are calculated based on initial monthly payments, your first year of payments, and your savings after four years should you choose an interest only, or fully amortizing ARM.
As you start talking to lenders, compare their proposals in the ARM vs. fixed rate mortgage calculator to see if you are receiving a good offer. Remember to save this great tool to your bookmarks and sign up to receive exclusive member benefits!