ARM vs. Fixed-Rate Mortgage
A lower ARM rate saves money early but carries reset risk. Compare it against a fixed-rate mortgage to weigh the trade-off.
How the arm vs. fixed-rate mortgage calculator works
This comparison runs an adjustable-rate loan beside a fixed-rate loan of the same size and term so you can weigh a lower opening payment against later uncertainty. The ARM side amortizes at its discounted start rate through the fixed period, then adjusts on schedule using index-plus-margin within its caps.
The fixed side keeps one rate and one payment for the whole term. Testing a flat, rising, and falling rate path shows how long the ARM's early savings last and roughly when a sustained climb would erase them.
Worked example: with loan amount of $320,000, loan term (years) of 30 and arm initial rate of 5.50%, the arm vs fixed rate mortgage calculator shows saved during the arm intro period of $15,515.
- ARM initial payment
- $1,816.92
- ARM payment after reset
- $2,186.48
- Fixed payment
- $2,075.51
- ARM lifetime interest
- $444,960
| ARM rate after reset | ARM | Fixed |
|---|---|---|
| 5.50% | $334,093 | $427,185 |
| 6.50% | $388,344 | $427,185 |
| 8.50% | $503,753 | $427,185 |
| 10.50% | $627,092 | $427,185 |
The better choice flips around 8.50% — ARM wins on one side, Fixed on the other.
The formula
Each loan amortizes its balance at its own rate over the term. The ARM payment changes at every reset to index + margin, bounded by the caps; the fixed payment never changes. Comparing cumulative interest and the payment at each reset shows the crossover where the fixed loan becomes cheaper.
- Both loans share the same principal, term, and start date so the difference reflects rate structure, not loan size.
- The ARM's start rate is the discounted teaser rate; real resets depend on future index levels you cannot know in advance.
- Rate scenarios are illustrative paths, not predictions, and actual benchmark moves may differ sharply from any path tested.
- Refinancing, selling, or extra principal payments before the fixed period ends would change the practical comparison.
- Closing costs, points, and mortgage insurance are excluded, though they can shift which option wins.
Results are estimates for educational purposes and are not financial advice. Confirm exact figures with your lender or a licensed advisor.
Questions about the arm vs. fixed-rate mortgage
How many years do I need to keep the loan for an ARM to pay off?
Often the break-even sits near or just past the end of the fixed period, but it depends on the rate gap at origination and how fast rates climb afterward.
If you are confident you will sell or refinance before the first reset, the ARM's lower start rate is close to free savings. The longer you hold past that point, the more rate risk you absorb.
Does a bigger rate gap between the ARM and fixed loan always favor the ARM?
A wider discount on the ARM start rate increases early savings and pushes the break-even further out, which leans toward the ARM. But it does not change the risk that rates rise after the fixed period.
A large gap is most compelling when paired with a short expected holding period, so the savings bank before any reset arrives.
What happens in this comparison if rates fall instead of rise?
In a falling path the ARM looks excellent: it starts lower and then resets even lower, widening its lead over the fixed loan. The catch is that you cannot count on that path.
A fixed loan gives you the option to refinance if rates drop, capturing much of the same benefit while protecting you on the upside if they climb instead.
Is the ARM vs. Fixed-Rate Mortgage free to use?
Yes. Every calculator on MortgageLoansCalculator is completely free, with no sign-up, login or paywall. Run as many scenarios as you like.
ARM vs fixed-rate — which should I choose?
A fixed rate is better if you will keep the loan for years and want a payment that never changes; an ARM can win if you will sell or refinance before its fixed period ends and want a lower starting rate. This tool compares the payments side by side.
Adjustable-Rate Mortgage (ARM) Calculator
Project payments through the fixed period and the rate adjustments that follow on an ARM.
ARM & Interest-Only ARM vs. Fixed
Compare a standard ARM, an interest-only ARM and a fixed-rate mortgage side by side.
Interest-Only ARM Calculator
Model the interest-only period of an ARM and the payment shock when amortization begins.
Option ARM Calculator
See how minimum payments on an option ARM can cause negative amortization and a growing balance.
Fixed-Rate vs. Interest-Only Mortgage
Compare a conventional fixed-rate loan against an interest-only mortgage over time.
Fixed-Rate vs. LIBOR ARM
Compare a fixed-rate mortgage with an index-based ARM under rising and falling rate paths.