Understanding the difference between a fixed and adjustable rate mortgage

16 April 2023

Choosing a mortgage is one of the biggest financial decisions a household will ever make, and the type of interest rate you pick shapes your budget for years to come. On this episode of The Housing Hour, we break down the difference between fixed-rate and adjustable-rate mortgages in plain language. Here's a practical guide to help you understand which option might fit your life.

What Is a Fixed-Rate Mortgage?

A fixed-rate mortgage locks in your interest rate for the entire life of the loan, whether that's 15, 20, or 30 years. Your principal and interest payment stays exactly the same from your first payment to your last, no matter what happens in the broader economy.

That predictability is the main appeal. If you buy a home with a fixed rate and market rates rise a decade later, you keep paying your original rate. If rates fall, you have the option to refinance, though that comes with closing costs and paperwork.

What Is an Adjustable-Rate Mortgage?

An adjustable-rate mortgage (ARM) starts with an introductory period during which the rate is fixed, often for 3, 5, 7, or 10 years. After that period ends, the rate adjusts periodically based on a benchmark index plus a margin set by your lender.

This means your monthly payment can go up or down when the rate resets. ARMs are often described with numbers like "5/1," which signals a five-year fixed period followed by adjustments once per year. Most ARMs include caps that limit how much the rate can rise at each adjustment and over the life of the loan, so it's important to read those terms carefully before signing.

The Trade-Offs at a Glance

Fixed-rate mortgage: Payment stability, protection against rising rates, but typically a higher starting rate.
Adjustable-rate mortgage: Lower initial rate and payment, but uncertainty after the intro period ends.
Both: Require attention to closing costs, loan terms, and your long-term plans.

Which Option Fits Your Situation?

The right choice depends less on the market and more on your personal circumstances. Ask yourself these questions:

How long do I plan to stay in this home? If you expect to move within the fixed period of an ARM, you may never experience an adjustment.
How stable is my income? Families with variable income often prefer the certainty of a fixed payment.
Could I afford the payment if rates rose to the allowed maximum? Stress-testing your budget against the worst case is essential with an ARM.
Do I value simplicity over potential savings? Fixed rates are easier to plan around; ARMs require more ongoing attention.

Common Misconceptions to Avoid

Many first-time buyers assume an ARM is "risky" in every scenario, or that a fixed rate always saves money. Neither is true. An ARM can be a sensible tool for a household with a clear, shorter timeline in the home. Conversely, a fixed rate can cost more over time if rates stay low and the borrower never refinances. The key is matching the loan structure to your actual plans, not to headlines or predictions.

Another mistake is ignoring the adjustment caps and index details on an ARM. Two ARMs with the same introductory rate can behave very differently after year five, so compare the full terms, not just the teaser number.

Final Takeaway

There's no universally "better" mortgage—only the one that fits your timeline, income stability, and tolerance for change. A fixed-rate mortgage rewards long-term stayers who prize predictability, while an ARM can reward those confident about a shorter horizon. Before you commit, run the numbers for both scenarios, ask your lender to walk through the adjustment terms line by line, and revisit the episode for the full conversation with our guests. Your future self—and your family's monthly budget—will thank you.