Fixed vs Adjustable Calculator

Are you looking for a fixed-rate mortgage or is an adjustable-rate mortgage (ARM) more your style? If you aren’t sure, run the numbers with our free fixed- vs. adjustable-rate mortgage calculator.

It can help clarify the financial difference between the two and may simplify your decision.


Weighing the pros and cons of a fixed rate mortgage vs. adjustable rate mortgage (ARM) can be complicated. To compare these options, factor in the length of the loan, when and how often adjustments occur, which index the lender will use, plus any assumptions about future interest rates. This calculator will make the process simple and walk you thru running the numbers.

Choose the length of time you expect to stay or when you might be ready to refinance.


The final price you expect to pay for the home.


You can enter a dollar amount or percentage. Some programs allow down payments as low as 3%. Just remember, the more you put down, the less your payment will be.

Choose the length of the loan term you plan to use. Standard loan terms are 15 or 30 years.


Enter the annual interest rate for a fixed rate mortgage.

Choose the length of the loan term you plan to use. Standard loan terms are 15 or 30 years.


Enter the initial annual interest rate for the adjustable rate mortgage.


Enter the number of months (1-360) before the first rate adjustment is applied. For instance, 5 years would correspond to 60 months.


Enter the number of months (1-480) between each subsequent rate adjustment. For instance, 1 year would correspond to 12 months.

Do you anticipate rates will increase, decrease or stay the same over the life of the loan?


The maximum amount the mortgage interest rate may increase with each adjustment.


The lowest interest rate that can be applied during the life of the loan.


The highest interest rate that can be applied during the life of the loan.


The benchmark interest rate that reflects current market conditions and is added to the fixed margin to calculate fully-indexed interest. The index rate is variable.


How much the interest rate can adjust up or down from one adjustment period to the next.


Enter the number of months between index rate adjustments.


A fixed percentage rate that is added to the index value to determine the fully-indexed interest rate.

These are the total costs of the loans over the years you have specified.

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These calculations are tools for learning more about the mortgage process and are for educational/estimation purposes only. Payment shown does not include taxes, insurance, or mortgage insurance (if applicable). This does not constitute an offer or approval of credit. Contact a PrimeLending home loan officer for actual estimates.

For example, a Conventional fixed rate loan with the terms purchase price of $312,500, on a loan term of 360 months, down payment of 20%, and an interest rate of 6.5%, will result in an annual percentage rate of 6.598% with $3,613 in APR fees. Rate pulled 09/02/22, rates change daily. Loans are subject to borrower qualifications, including income, property evaluation, and final credit approval.



A fixed-rate mortgage offers borrowers an interest rate that does not change over the length of their loan. Some benefits of fixed-rate mortgages include predictable monthly payments, protection from market changes and a wide range of product options. Common fixed-rate mortgage terms are 15- and 30-year mortgages.

A 30-year fixed-rate mortgage is considered a long-term mortgage and often offers some of the lowest monthly payments available as the payments are spread out over a longer period of time. Alternatively, a 15-year fixed-rate mortgage is considered a short-term mortgage which offer somewhat higher monthly payments compared to the 30 year mortgage.


An adjustable-rate mortgage (ARM) has an interest rate that changes over the life of the loan. After your introductory period is over, the rate on an ARM will change according to the market which means if market rates lower, so does the rate on your mortgage.

Often you will see ARM’s shown as X/Y with X being how many years of your fixed initial rate and Y representing how often your rate will change (in either years or months) throughout the remainder of your loan. Every lender is different, however some offer a range of ARM terms including 5/6, 7/6, 10/6 and 15/6.


Fixed-rate mortgages and ARMs work differently so it is important to know which one will work best for your plans. That’s where a fixed- vs. adjustable-rate mortgage (ARM) calculator can help you compare the potential cost of each option. The key difference between a fixed- and adjustable-rate mortgage is that a fixed-rate mortgage has a set interest rate through the life of the loan while an ARM’s interest rate can change (possibly more than once) throughout the life of the loan.

Here’s a side-by-side comparison of fixed- vs. adjustable-rate mortgages:

Fixed-rate mortgages

  • Interest rate never increases
  • Predictable monthly payments
  • Long- or short-term options
  • Low monthly payments on long-term loans

Adjustable-rate mortgages

  • Lower initial interest rate
  • Lower starting monthly payments
  • Possibility of affording more space
  • Could pay less in return (in favorable market conditions)


When you’re trying to choose between a fixed-rate mortgage or an ARM, your desired interest rate now, and in the future, may factor into your choice. What if we told you that you could refinance either option down the road? That’s right. You can refinance your fixed-rate mortgage or your adjustable-rate mortgage (ARM) in the future.

How does it work? Imagine the day comes that you are still in love with your home, but not your mortgage rate. You can refinance your fixed-rate mortgage to another fixed loan or you can choose to refinance to an ARM and vice-versa; you can refinance your adjustable-rate mortgage to another ARM or to a fixed rate.

The process of refinancing either a fixed-rate mortgage or an ARM is very similar to the process of getting your initial mortgage, only this time you might have some home equity that you can tap into. A refinance can help you turn your home equity into cash that you can use any way you choose. Need a new roof? A refinance could help. Want to go on a vacation? A refinance could help get you there.

Before you refinance, it’s important to talk to your PrimeLending loan officer about your options and if you are better off refinancing to a fixed-rate mortgage or to an ARM.