ARMS Defined

1560492_10151836164426046_1986095200_nAdjustable Rate Mortgages, also referred to as ARMs, come in many shapes and sizes.  This post will be focusing on fixed period ARMs, such as the 3/1, 5/1, 7/1, 10/1…etc. that feature a fixed rate period before adjusting.

We’ll pick on the 5/1 ARM to make things easy.   The first digit (5/1) is how long the initial rate period is fixed for.   With the 5/1 ARM, that would be 5 years or 60 payments.   The second digit (5/1) is how often the ARM will adjust after the fixed period (at the 61st payment with a 5/1 ARM).   Your rate will continue to adjust once a year on the anniversary of the first adjustment date.

You may also see 5/6 ARMs, that means the payments will adjust every 6 months instead of once a year.

You also need to know what your CAPS are.   The CAPS are in place to restrict how high or low your ARM can adjust.   And just like ARMs, they can vary too.   Common CAPS are 5/2/5 or 2/2/6 for the 5/1 ARM.

The first digit with the CAPS (2/2/6), is how much the interest rate can adjust at the first adjustment point.   So, if you have a 5/1 ARM, with 2/2/6 CAPs, your rate may adjust up or down no more than 2% at the first adjustment date.   If you have 5/2/5 CAPS, the rate could adjust no more than 5% up or down.

The second digit of the CAPS (2/2/6), is how much the rate may adjust up or down after the first adjustment every adjustment point thereafter (once a year, if you have a 5/1 ARM; every 6 months if  you have a 5/6 ARM).

The last digit of the CAPS (2/2/6), is the most the the rate could ever adjust to – also referred to as the ceiling. This is determined by adding the last digit to the original note rate. If your original note rate (before any adjustments) during the fixed period is 5 percent, the highest the rate could ever be during the term of the mortgage would be 11 percent.

When your fixed period is over, your rate will adjust based on what your mortgage balance is at the adjustment time (60 months, per this example).   The formula for this is preset by the margin to the index.  The index may be based on several options.   The margin may vary as well such as 2.25% – 2.875% for prime mortgages (subprime mortgages and option ARMs may have larger margins).

Your rate and payment can adjust downwards as well depending on the performance of the index your ARM is based on.   Interest only ARMs are a different animal.  The caps and margins still work the same.  The big difference is how long the interest only period is (when the amortization of the mortgage begins)…I will follow up on this on another post.

With ARMS, it’s important to find out from your Mortgage Planner what your CAPs are and what the margin is.  This should be disclosed on your lock confirmation.   However, this may be something you wish to find out from your Mortgage Planner well in advance, especially if your comparing ARM rates, you should have the entire picture to compare apples to apples (or should I say, arms to arms).

ARMs can be great financial tool if someone considering not retaining the property or the mortgage for a long term and if the rate is advantageous over a product such as the 30 year fixed rate.

Click here for a rate quote for homes located in Washington state.


  1. I’m aware that this is an old article but this advice is wrong:
    The last digit of the CAPS (2/2/6), is the highest the the rate could ever adjust to; the ceiling.

    The last digit is the maximum amount that the interest rate can *change*. So if your note rate is 4% and your lifetime cap is 6%, your ceiling rate would be 10%, not 6%.

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